Radical initiators and chain extenders for converting methane gas into methane-sulfonic acid

ABSTRACT

Improved initiators, solvents, and SO3 mixtures are disclosed which can increase the yields and efficiency of a process which converts methane gas into methane-sulfonic acid (MSA). MSA is valuable in its own right, or it can be processed to create desulfured fuels and other chemicals. Preferred initiators have been identified, comprising at least one “primary” initiator, and at least one “extender” (or secondary, supplemental, enhancing, tuning, tweaking, or similar terms) initiator. “Primary” initiator(s) include (unmethylated) Marshall&#39;s acid, mono-methyl-Marshall&#39;s acid, and di-methyl-Marshall&#39;s acid, while a secondary/extender initiator comprises methyl-Caro&#39;s acid, which can oxidize sulfur DI-oxide (an unwanted chain terminator) into sulfur TRI-oxide (an essential reagent). Other enhancements to the MSA manufacturing process also are described.

RELATED APPLICATIONS

This application is a continuation-in-part of both:

(i) U.S. application Ser. No. 15/917,632 (which described certainchemical initiators which can trigger a radical chain reaction asdescribed herein), which was filed on Mar. 10, 2018, and which claimed apriority date under 35 USC 119, based on provisional application62/601,084, filed on Mar. 10, 2017; and,

(ii) U.S. application Ser. No. 15/917,631 (which relates to anintegrated processing system which uses the same initiators and radicalchain reaction described herein), also filed on Mar. 10, 2018, whichclaimed a priority date under 35 USC 119, based on provisionalapplication 62/601,065, filed on Mar. 10, 2017.

All applications cited above were invented and owned by the sameinventor/applicant. Certain information relevant to the initiatorsdescribed and claimed below was inadvertently placed in provisionalapplication 62/601,065, which relates to the integrated processingsystem rather than the initiators. By citing all four parent applicationlisted above, the priority-dated information which is relevant toinitiators is being straightened out and clarified, for discussionherein.

BACKGROUND

This invention is in the fields of organic chemistry, and oil and gasprocessing, and relates to methods for converting methane gas into aliquid compound called methane-sulfonic acid (MSA), which is valuable:(i) in various industrial processes, such as certain types of metalprocessing; and, (ii) as an intermediate reagent for “downstream”processing, which can create sulfur-free liquid fuels and othercompounds while retaining the sulfur reagents on site, so that they canbe used to continue making more MSA.

An important new chemical method for converting methane gas into liquidfuels and other valuable chemicals is described in U.S. Pat. No.7,282,603, by the same Applicant/Inventor herein. Briefly, methane (CH4)is contacted with a “radical initiator” compound which is strong enoughto rapidly remove an entire hydrogen atom (both the proton, and theelectron) from a molecule of methane. This creates a methyl radical,written herein as H3C*, where the asterisk represents an unpairedelectron. If the reaction mixture is properly controlled, the methylradicals will attach themselves to sulfur trioxide (SO3) in a specialreaction mixture, thereby forming an unstable radical version of acompound called methane-sulfonic acid, abbreviated as MSA.

The unstable MSA radicals have enough strength to then attack a freshmolecule of methane, and remove a hydrogen atom from that new moleculeof methane. That reaction will create both:

(1) a complete and stable molecule of MSA, with the formula H3CS(O2)OH,as a liquid which will be pumped out of the MSA-forming reactor; and,

(2) a newly formed methyl radical, which will immediately attach itselfto a new molecule of SO3, inside the reactor.

In this manner, a small quantity of a “radical initiator” compound caninitiate (or trigger, commence, launch, or similar terms) a chainreaction. Under optimal conditions, that chain reaction will keep goingfor dozens, hundreds, or even thousands of cycles, so long as freshmethane and SO3 continue to be pumped into the reactor vessel.

The output, from that reactor vessel, will be a stream of MSA, which isformed by the following balanced reaction:CH4+SO3→H3C—S(O2)OHMethane+sulfur trioxide→methane-sulfonic acid

The MSA will be in liquid form, and the “radical chain reaction”described above can create an MSA output stream which is remarkablypure, compared to all known prior efforts to process methane gas intoliquids.

Anyone interested in this invention should realize that very largequantities of “stranded” or “waste” methane gas are wasted anddestroyed, and are effectively valueless (or, even worse, must betreated as extremely dangerous waste products) at numerous locations.Compared to crude oil, methane gas is a very “thin” fuel, with very lowenergy density; even without the increased energy content of thesubstantially larger hydrocarbon molecules in crude oil, the simple factthat methane is a gas, while crude oil is a liquid, means that theenergy content of a given volume of methane gas, even when underpressure, is less than 1/100th of the energy content of a comparablevolume of crude oil. As a result, most “stranded” or “remote” oilproduction locations (such as offshore oil platforms) simply do not haveany pipelines, at all, to handle the methane gas which will emerge fromthe crude oil, after the crude oil has been brought up from thetremendous pressures in an underground reservoir, to the surface. As aresult, that methane gas must be treated as a hazardous, dangerous,explosive by-product of the oil production. At such locations, roughly$100 million worth of “waste” methane is burned, every day, in flares,and the functional definition of “flare” is, “a device which burns aflammable fuel, without deriving any value or benefit from the energycontent of that fuel”. The worldwide practice of “flaring” waste methanepumps huge quantities of carbon dioxide (and heat) directly into theatmosphere, in ways which contribute directly to climate change andglobal warming without gaining any offsetting benefit.

In addition, large quantities of methane are released at livestockfacilities, and at coal mines and various other sites where methaneseeps out of the ground, or is generated as a byproduct of eithernatural or industrial processes.

Although methane is a highly valuable fuel when it can be captured andtransported to locations that need and use it, at locations where it is“stranded”, flared, or otherwise wasted or under-utilized, it can beregarded and treated as an essentially free resource. Accordingly,facilities which can use the new radical chain reaction to convertmethane into MSA and other liquids, which can be transported by tankeror pipeline, offer enormous potential for industrial, public, andenvironmental benefits.

MSA (i.e., the acidic liquid which is created by the radical chainreaction mentioned above) is used in various industrial processes, suchas electroplating and semi-conductor manufacturing. However, thosemarkets are relatively small, compared to the huge market forclean-burning liquid fuels. Therefore, after the infrastructure formaking MSA from methane passes a baseline capacity, most of the MSAformed by the “radical chain reaction” described above is likely to beprocessed in ways referred to herein as “downstream” processing. Becauseof several factors (including the fact that MSA has a direct bondbetween the carbon atom and the sulfur atom), MSA is well-suited forcertain types of chemical processing (including catalytic processing,using various types of porous solids, particulate beds, etc.) which willremove the sulfate group (usually in the form of sulfur dioxide, SO2)from the MSA. This will allow the methyl group of MSA (i.e., H3C—) to beconverted into any of several desulfured fuels that are suited forshipping to any desired site via tanker, pipeline, or similarconventional means. Such fuels include methanol, dimethyl ether, andeven gasoline, and the types of “downstream processing” that can be usedto convert MSA into such final products is described in other patentapplications by the same Applicant herein.

This current invention relates to the “radical chain reaction” which isused to convert methane (a gas, under any normal conditions) into MSA (aliquid). As is well known to chemists, a crucial problem which hinders,limits, and reduces the efficiency and output of any industrial-scale“chain reaction” can be summarized by the phrases, “chain termination”and “chain terminators”. Both phrases refer to the fact that, in nearlychain reaction which has been running continuously for a sustainedperiod of time:

(i) small quantities of unwanted impurities will gradually be formed orreleased, inside the reactor vessel where the chain reaction is takingplace; and,

(ii) as indicated by the name, any compound which functions as a “chainterminator” can abruptly stop a chain reaction, after only a limitednumber of cycles. Usually, that type of chain termination occurs becausean unwanted impurity or byproduct, inside a reactor, will react with andinactivate (other terms, such as quench, neutralize, poison, deplete,exhaust, etc., also can be used) one of the unstable molecular “species”which is necessary to keep a chain reaction going.

By definition, whenever a “chain terminator” is present inside a reactorthat is running a chain reaction, the chain reaction will fall short(often far, far short) of the number of cycles that could be achieved,if the “chain terminator” could be eliminated. In most cases, the mostdirect and efficient ways to eliminate “chain terminator” species is byeither: (i) preventing them from being formed, inside a reactionmixture; and/or, (ii) adding an additional reagent to the reactionmixture, to absorb or inactivate the chain terminator(s) withoutstopping the chain reaction.

A hypothetical example can illustrate how important and valuable it canbe to: (i) identify any “chain terminators” that are hindering a chainreaction, and then (ii) find some way to either prevent them from beingformed, or to eliminate them quickly if and when they form. For thepurpose of analysis, assume that:

(1) the presence of a certain “chain terminator” will stop a chainreaction after an average number of cycles that is somewhere in therange of 50 cycles, in a certain reactor vessel; and,

(2) that same chain reaction would keep going for an average of 200cycles, if the chemists and/or engineers responsible for it can findsome way to eliminate that chain terminator.

If the chemists and engineers can get rid of a chain terminator, in away which boosts the average cycle numbers from 50, up to 200, then theywill, quite literally, quadruple the quantity of the desired outputproduct which is being created by their reactor.

Those types of numbers are not unrealistic; indeed, they understate thecase, compared to many real chemical processes that rely upon chainreactions. Elimination of “chain terminators” can reduce the costs,increase the yields, and increase the profits from such reactions, oftenby a large margin (and in some cases, by an outright multiple).

Accordingly, the invention disclosed herein arises from the discoveryand realization that a specific chemical species, sulfur DI-oxide (SO2),was causing serious levels of chain termination, inside the testreactors that were being used to convert methane gas into liquid MSA,when certain types of previously disclosed “peroxide initiators” werebeing used. Therefore, the teachings herein describe how to prevent theformation of sulfur dioxide, and/or how to neutralize any SO2 byconverting it into other NON-chain-terminating molecules, inside areactor that is using a radical chain reaction to convert methane intomethane-sulfonic acid.

As background information which can help readers better understand theinvention herein, two additional subsections are provided below. Onesubsection is on the crucial differences between SO2 (i.e., sulfurDI-oxide), an unwanted chain terminator, versus SO3, sulfur TRI-oxide,which is an essential reagent for the chain reaction. Understanding thatdifference requires the reader to do more than just notice that SO3 hasone more oxygen atom than SO2. Instead, a crucial difference in theirshape, and their surface-accessible electron arrangements, causes SO2 tobe a highly unwanted by-product that is effectively “toxic” to thedesired reaction, while SO3 is the perfect and ideal reagent fordriving, enabling, and supporting the reaction.

The second subsection is on peroxide compounds in general, and on thetypes of specialized peroxide compounds that can be used to initiate themethane-to-MSA chain reaction.

Two more prefatory comments are offered at this point, before gettinginto the substance of this invention. First, the chemical name“methanesulfonic acid” should be methyl-sulfonic acid, either with orwithout a hyphen. For unknown reasons, industry practice settled on thename “methanesulfonic acid”, decades ago, and that is how it is referredtoday, by the chemical industry. To help make it easier to recognizequickly, while distinguishing it from other similar or relatedcompounds, MSA is spelled herein with an inserted hyphen, asmethane-sulfonic acid. The name “methyl-sulfonic acid” should beregarded as entirely correct and appropriate in all uses, and as MSAbecomes more important and well-known, it is hoped that that correctphrase will gradually replace the incorrect version.

The second convention used herein is to simply spell out chemicalformulas, when placed in lines of normal text, without using subscriptfonts for the numbers. For example, instead of writing the chemicalformula for MSA as H₃CSO₃H, or as H₃CS(O₂)OH (both of which are correct,and involve two different but well-known chemical practices), it iswritten herein simply as H3CSO3H. Similarly, sulfur dioxide is writtenherein simply as SO2, sulfur trioxide is written as SO3, and methane iswritten as CH4. This is because text-only versions of patentapplications (as published on the USPTO website, with helpfully numberedparagraphs) can be copied and then pasted into text-only “Notepad”files, which can be extremely handy, helpful, and useful, above andbeyond the published “pdf” versions that can be downloaded (at no cost)from Google Patents and elsewhere. Subscript fonts in chemical formulasclutter up and entangle text-only files. Therefore, they are kept to aminimum herein, since anyone can readily grasp and understand that anynumber that appears in these types of chemical formulas simply indicateshow many copies are present of the immediately preceding atom.

SO3 is a Reagent; SO2 is a Terminator

Sulfur contains 6 “valence” electrons (i.e., electrons in its outermostshell; “valence” electrons are the only electrons, in any atom, whichcan form bonds with other atoms, to form molecules). One electron willbecome involved in each single bond that sulfur forms with some otheratom; and, two electrons will become involved in any double bond thatsulfur forms, with an atom such as oxygen.

When a sulfur atom forms sulfur DI-oxide (SO2), four of its sixelectrons will become involved in the two double bonds, and the othertwo electrons remain free and accessible. This gives SO2 the followingstructure and arrangement, with its two oxygen atoms forming a 119degree angle between them:

The two “free electrons” which belong to the sulfur atom are not merelypartially or somewhat accessible; instead, they are prominently exposed.This is analogous to saying that if something flexible is draped acrossthe rounded back of a sofa, whatever is on top of it will become evenmore exposed and accessible.

Sulfur DI-oxide is not a stable molecule, because the sulfur cannotreach or satisfy the so-called “octet rule”. That rule applies to the“outermost” or “valence” electrons, among elements in the top rows ofthe “periodic table” (i.e., the chart of elements which is familiar tohigh school and college chemistry students). As a very brief overview,the elements in the top rows of the periodic table will seek to formmolecules and/or ions which will enable them to have either zeroelectrons, or 8 electrons, in their outermost “valence” shell. Thevarious elements can reach that goal and satisfy “the octet rule” byeither of two mechanisms:

(i) An element will form a specific number of bonds with other atoms,where a “single bond” effectively provides one additional electron, anda “double bond” effectively provides two additional electrons. Forexample, since carbon begins with 4 electrons of its own, it will seekto form 4 bonds with other atoms; that is why molecules such as methane(CH4) and carbon dioxide (O═C═O) are stable. Since nitrogen begins with5 electrons of its own, it will seek to form 3 bonds with other atoms;and, since oxygen begins with 6 electrons of its own, it will seek toform 2 bonds with other atoms.

(ii) Alternately, some elements become ionic, by either: (a) “shedding”(or donating, or similar terms) one or sometimes two electrons, andbecoming positively charged, if they are near the left side of theperiodic table; or, (b) by taking electrons away from other elements(and becoming negatively charged), if they are near the right side ofthe periodic table. As a simple example, normal table salt (sodiumchloride, NaCl) will adopt an ionic form whenever it is dissolved inwater, with Na⁺ ions (sodium, on the far left side of the periodictable, satisfies the octet rule by getting rid of its single valenceelectron) and Cl⁻ ions (chlorine, near the far right side of theperiodic table, with 7 out of the 8 electrons it needs, satisfies theoctet rule by taking an electron away from some other atom).

There are a relatively small number of known exceptions to “the octetrule”, involving molecules which do NOT satisfy that rule, but whichnevertheless exist and persist in nature for extended periods of time(such as days or weeks, under suitable conditions). These unusualmolecules are usually referred to as having “resonant” structures, andthey tend to be unstable, highly reactive, and dangerous. Sulfur dioxideis one example; carbon monoxide, the toxic and poisonous gas, isanother.

Sulfur TRI-oxide (SO3) is more complex than SO2, and it can take severaldifferent forms, in which several molecules of SO3 will form clusters,or aggregates, which can have certain known and predictable shapes andstructures, as described below. If and when it exists as a “monomer”,SO3 has a relatively flat triangular shape, similar to sulfur DI-oxideexcept that the two free and unpaired electrons, on SO2, will becomepart of a double-bond that will be formed when an additional oxygen atom(i.e., the “third” oxygen atom) arrives and is added to the molecule.

As with SO2, it should be noted that SO3 also does not satisfy “theoctet rule”, unless the viewer decides to regard all of its electrons asbeing assigned to the three oxygen atoms, in which case the sulfur atomat the center of an SO3 molecule can be said to reach a +6 oxidationstate. That is not an invalid way to regard it; oxygen sits directlyabove sulfur in the periodic table, and is more “compact andconcentrated”, in a very real sense. Among other factors, electrons inthe “valence shell” of an oxygen atom are substantially closer to thenucleus than the valence electrons of sulfur atoms. The six atoms ofoxygen have nothing but two internal electrons (in what is usuallycalled “the s shell”, sometimes called as “the helium shell”) betweenthe valence electrons and the nucleus. By contrast, the valenceelectrons in sulfur surround a completely full orbital cloud of anadditional eight electrons, in addition to the two innermost electronsin “the helium shell”. The fact that the valence electrons in sulfursurround not just one but two completely full intervening orbital shellsof electrons, render the attraction between sulfur's valence electrons,and its nucleus, substantially less direct and less powerful, than thevalence electrons in oxygen. Just as two magnets, when held closetogether, exert a stronger pull than the same two magnets when heldfarther apart, the “gripping strength” of valence electrons issubstantially stronger, in elements that appear in the top row of theperiodic table.

As a result of various factors, SO3 is relatively unstable and reactive,and it can be extremely difficult to handle. Among other problems, itcan take any of three different arrangements, as mentioned above, inwhich several molecules of SO3 will combine with each other, to formclusters or aggregates. In pure liquid SO3, the smallest and mostreactive aggregate, called “gamma” SO3, is created when 3 molecules ofSO3 join together to form a 6-member ring, with sulfur and oxygenalternating with each other in the ring, and with the other 6 oxygenatoms attached to the three sulfur atoms. Therefore, “gamma SO3” has aformula of S3O9, and is nicely illustrated in the Wikipedia entry onSO3.

Since this “gamma” form is the most reactive form of SO3, it willdegenerate over time into the alpha or beta forms, which are strandedand fibrous aggregates, rather than rings. Those stranded forms are morestable and less active than the gamma form. When a molecule shifts intoa more stable form, it becomes less reactive, and therefore less usefulas a chemical reagent, if the desire is to convert that reagent intosomething else (as distinct from using it as a solvent, etc.).

In addition, SO3 can rapidly and spontaneously convert into sulfuricacid, if any water (such as atmospheric humidity, for example) isallowed to reach the SO3.

To minimize and cope with the very difficult handling problems thatarise when pure SO3 is used in industrial or laboratory settings, SO3 isusually mixed with sulfuric acid, under controlled conditions, to createa mixture called “oleum”. When sulfuric acid and SO3 are mixed together,they create a “dimer” compound with the formula H2S2O7, which is calledeither “di-sulfuric acid” or “pyrosulfuric acid”. It is a meta-stableintermediate which can break apart quickly and easily, when oleum isdiluted to allow the SO3 to react with something else.

The percentages of SO3 and sulfuric acid vary, in the mixtures that arecalled “oleum”; therefore, at least one number (usually representing theweight percentage of the SO3 in the mixture) must be specified, to letothers know what type or grade of oleum is being discussed. Commonlyavailable weight ratios range from 10% SO3, up to more than 60% SO3.Oleum is highly toxic and corrosive, and becomes even more so if wateris allowed to contact it. Therefore, it requires great care in storage,shipping, and handling.

The bottom line is that a major part of what enables SO3 to react,rapidly and efficiently, with any methyl radicals that are in a reactionmixture which is designed and run in a way that will create MSA, is acombination of:

(i) the inherent instability and reactivity of the SO3; and,

(ii) the very large number of “unshared electron pairs” that belong tothe oxygen atoms which surround and enclose a molecule of SO3.

If a single molecule of SO3 is regarded as having the sulfur atom in thecenter, surrounded by three oxygen atoms in a flat triangulararrangement, each of the three oxygen atoms will have not just one buttwo complete pairs of “unshared electrons” on its exposed outer surface.This creates a total of six pairs of “unshared electrons” (i.e., 12electrons in all, arranged in six pairs) on SO3. This effectivelycreates a large and powerful “electron cloud” that surrounds eachindividual molecule of SO3.

Extending that concept to larger numbers, if three molecules of SO3 forma “gamma” aggregate as described and illustrated above, with the formulaS3O9, that gamma aggregate will have a total of 36 unshared electrons,arranged in 18 pairs. This will generate an even larger “electron cloud”around that molecule, with negative charges.

If “methyl radicals” (each having the formula H3C*, where the asteriskrepresents an unshared or “singlet” electron) are present in a reactionmixture that also contains SO3 (either in single-molecule SO3 form, orin a gamma-aggregate S3O9 form), the methyl radicals will be stronglyattracted to the SO3 for not just one but two reasons. First, the threehydrogen protons, on the surface of any methyl radical, will create alocalized positive charge, which will be directly attracted to thenegatively-charged electron cloud which will surround either the solo oraggregated SO3. And second: the unpaired singlet electron, on any methylradical, will be aggressively attracted to any electron cloud, since acluster of electrons will allow the singlet electron to effectivelymerge with, and blend in with, an entire group of electrons, in a mannerwhich will become more stable than a methyl radical all by itself.

Accordingly, that type of attraction, between a methyl radical and anSO3 molecule or aggregate, will lead to a fast and efficient reaction,in which:

(i) the methyl radical will initially attach itself to the SO3, therebyforming a transitional intermediate; and,

(ii) that transitional intermediate will then rearrange itself, in amanner which consistently and reliably creates a radical form ofmethane-sulfonic acid (MSA).

That MSA radical will have just the right amount of strength andinstability to cause it to attack a “fresh” molecule of methane (i.e.,CH4), so long as fresh methane is being added continuously to thereaction mixture. That type of attack will cause an MSA radical torapidly and efficiently take away, from a methane molecule, one of itshydrogen atoms (i.e., both the proton AND the electron, which is ideal,rather than just the proton, which would create an unhelpful andunproductive ion). That leads to the formation of a complete and stablemolecule of methane-sulfonic acid (MSA), which is the desired product ofthe reaction. In addition, and crucially, that attacking reaction alsocreates a brand new methyl radical, which is exactly what is needed tokeep the radical chain reaction going for another cycle.

In direct contrast to that ideal system, which will keep the chainreaction going (and making more and more of the desired product, MSA) solong as fresh SO3 and methane continue to be pumped into the reactor,SO2 (sulfur DI-oxide) will have the exact opposite effect, if it is alsopresent inside the reactor. Instead of keeping the chain reaction going,SO2 will terminate a chain reaction, and bring it to an abrupt halt,thereby eliminating it as a reaction which can contribute to creatingmore MSA, inside a reactor. SO2 does so by creating one or moreundesirable and unhelpful methyl-sulfate intermediates, which will nothave the shape, strength, or reactivity that will enable them to either:(i) make MSA, or (ii) react with fresh methane to convert it into newmethyl radicals.

Even if only small quantities of SO2 are created within the reactor,their activity as “chain terminator” molecules can seriously impair theefficiency, and reduce the output and yield, of the desired chainreaction. For example, even a small percentage of SO2, in the reactionmixture, may be able to reduce the average number of cycles which thechain reaction is able to achieve, from a relatively high number (suchas 200 to 500 cycles) down to a much lower number (such as 30 to 50). Tocontinue that example, if the average number of cycles is reduced from,say, 300, down to 50, then only ⅙th as much MSA will be formed, for eachand every chain reaction that is triggered by a “radical initiator”molecule.

As a final point worth noting, one cannot compensate forchain-terminating problems by simply pumping in more radical initiators.To begin to understand why not, one should begin by noting that thetypes of “radical initiator” molecules which can be used to rapidly andeffectively convert methane (CH4) into methyl radicals (H3C*) should beregarded as “extremely, extra-ordinarily hyper-expensive” when the costsof the reaction are considered and evaluated. This arises directly fromtheir extremely and aggressively acidic, corrosive, unstable and toxicnature. Even if their beginning ingredients were cheap, the costsrequired to make and then handle these particular compounds in reliablysafe and effective ways are extremely high. As a first example,Marshall's acid (one of the types of initiators of interest herein) is atype of peroxide, formed from concentrated sulfuric acid; an alternatename for it is peroxy-di-sulfuric acid. It is, simply put, concentratedsulfuric acid which has been turned into a two-part “dimer” byconnecting two sulfuric acid radicals to each other, via an unstableperoxide bond, which will indeed break apart, to release both of thosetwo sulfuric acid molecules, in even more unstable and aggressiveradicalized forms. So, to develop a mental handle on what is going on inthese types of reactions, using these types of initiators, one can startby seriously pondering the corrosiveness and aggressiveness of sulfuricacid, and then doubling those factors.

Furthermore, if a “chain terminator” such as SO2 is present (even at lowlevels) in a batch of MSA which is being manufactured, it can seriouslydegrade the quality of the MSA, and its value to prospective purchasers.This can sharply increase the costs of purifying any “rough” MSA to alevel which will make it truly valuable to purchasers, and it can createsubstantial and even large quantities of highly corrosive and toxicwastes and byproducts, which will need to be handled and reprocessed,somehow.

Therefore, if SO2 (or other chain-terminating species) in amethane-to-MSA reactor can be prevented from forming (or, if a“quenching” compound can be added to the reaction mixture, which willneutralize or eliminate any SO2 without hindering the methane-to-MSAconversion), the efficiency, yield, economics, and profitability of thereaction can be substantially improved. That is what the “initiatormixtures” disclosed below are intended—and able—to achieve.

Peroxide Compounds, in General

In industrial and commercial settings (i.e., where high-speed, low-costreactions are important), the “radical initiator compounds” thatnormally will be used, to initiate the chain reaction which will bondmethane to SO3 in a manner which forms MSA, will fall within a class ofchemicals known as peroxides.

Since the choice and selection of certain specific peroxide compoundslies at the heart of this invention, background information on peroxidecompounds in general is provided below; and, that information isfollowed by more specific information on the particular types ofperoxide compounds that previously were disclosed for use in initiatingthe radical chain reaction that converts methane into MSA.

In chemistry, peroxide compounds are characterized by having two oxygenatoms directly linked to each other, in a form which can be written invarious ways, including:

R1OOR2, in which R1 and R2 are “variables” (comparable to X or Y, in analgebraic equation) which can represent hydrogen, or any other atom oratomic group. The letter “R” was chosen as the variable for these typesof chemical formulas, since that atom or atomic group would be a“radical” if it were separated from the rest of the compound.Alternately, it may be helpful to think of “R” as representing the“residue” of whatever reagent was used to create the compound ofinterest. The subscripts 1 and 2, in R1 and R2, are used to distinguishbetween and identify the two different radicals/residues, so that eachone can be tracked and followed accurately, through any subsequentreactions.

R1O—OR2 is exactly the same formula as above, but with the bond betweenthe two oxygen atoms shown explicitly, to emphasize the peroxide natureof the compound, and to make it immediately clear, to chemists, that thecompound is not an ester, carboxy, or similar compound which involvestwo oxygen atoms that are in close proximity, but not in a peroxidearrangement.

R1-O—O—R2 also is the same formula, showing more bonds.

X—O—O—Y (or XO—OY, or XOOY) is the same formula, but with X and Y(instead of R) used as the variables. As variables, X and Y (as with R1and R2) can represent different types of atoms or groups, or they canrepresent the same type of atom or group (such as in HOOH, which ishydrogen peroxide, or H3C—O—O—CH3, which is dimethyl peroxide).

Peroxide compounds are generally preferred, for converting methane (CH4)into methyl radicals (H3C*), because “the peroxide bond” (i.e., the bondwhich connects two oxygen atoms to each other), in some (but not all)types of peroxides, can have an ideal balance and combination of traits,with each and all of the following factors:

(1) Peroxide bonds are stable enough to endure for sustained periods oftime, allowing at least some types of peroxide compounds to be storedfor weeks or months. Examples include the bottles of hydrogen peroxide(HOOH) that can found on any drugstore shelf. The bottles which holdH2O2 in stores are made of heavy opaque plastic, to keep any light fromreaching the peroxide compound inside the bottle. Basic normal light canbreak large numbers of the peroxide bonds in hydrogen peroxide, over aspan of weeks or months, which is a common shelf life for bottles ofhydrogen peroxide in drugstores.

(2) Despite having some level of stability, peroxide bonds also aresufficiently UN-stable, and reactive, to rapidly break apart, andrelease large numbers of aggressive “radicals”, as soon as their stablestorage conditions are altered. This is evidenced by the way that thesame hydrogen peroxide which remained stable for months, while sittingin an opaque bottle on a shelf in a store and then a bathroom, suddenlybecomes an aggressively active disinfectant, which will attack and killmicrobes, as soon as the hydrogen peroxide is taken out of that bottleand spread across an area of damaged skin.

(3) In industrial usage, peroxide bonds can be broken apart at preciselycontrolled times, exactly when the radicals are needed, by means such aspassing a peroxide liquid through a short segment of tubing made from asuitable transparent material. Specialized types of glass,polycarbonate, or polyacrylic are used in these settings, since theyallow ultraviolet (UV) radiation or “tuned” laser light to pass throughthose transparent materials in a wall, window, or tubing segment. Theenergy input provided by incoming ultraviolet or laser radiation willbreak at least some of the peroxide bonds, releasing radicals.

Alternately or additionally, heat energy can be used to break peroxidebonds; therefore, if a well-chosen peroxide liquid is injected into ahot mixture (this can include relatively mild heat, which in organicchemical processing generally refers to temperatures below the boilingpoint of water), the heat can serve as a sufficient “activator” to breakperoxide bonds, in a manner which will release radicals into thechemical mixture, to initiate a desired chemical reaction.

(4) Finally, because of their definition and nature (i.e., peroxidebonds necessarily involve TWO oxygen atoms, bonded directly to eachother), breakage of any peroxide bond will release not just one but TWO“radical oxygen species”, each of which can be written as RO*, or R1O*,or XO*, where the asterisk refers to an unpaired electron (also called a“singlet” electron) that will remain attached to each oxygen atom.Furthermore, that singlet electron, on an exposed surface of the oxygenatom, will be directly exposed, accessible, and ready to react withanything it can attack, as soon as the peroxide bond is broken.

One item of terminology used herein needs to be mentioned. As used inthe claims, any reference to “peroxide component” refers to either orboth of the two molecular fragments or portions that will be released,by a peroxide compound, when the peroxide bond is broken. If a peroxidecompound can be written and described by the formula R1O—OR2, where eachof R1 and R2 represent any type of atomic or molecular group orconstituent, then one of the “peroxide components” will be R1O*(including the oxygen atom, and its unpaired “singlet” electron) and theother “peroxide component” will be *OR2 (including the oxygen atom, withits unpaired “singlet” electron). Similarly, if a peroxide compound canbe written and described by the formula XOOY, where X and Y arevariables that can represent any atomic or molecular group orconstituent, then one of the “peroxide components” will be XO*, and theother “peroxide component” will be *OY.

Marshall's Acid, Caro's Acid, and DMSP

Because of various factors, most of the commonly used and relativelymild peroxide compounds (such as hydrogen peroxide, written as HOOH orH2O2) are not strong enough to rapidly and efficiently extract acomplete hydrogen atom (both the proton, and the electron) from methane(CH4), in a manner which will convert the methane into a methyl radical(H3C*).

Therefore, stronger and more powerful peroxides are required, to convertmethane gas into methyl radicals. The peroxides of primary interestherein contain sulfur, and, in most cases, are variants of sulfuricacid, H2SO4, which also can be written as HO—S(O2)-OH.

If two molecules of sulfuric acid are combined and converted into aperoxide, the resulting compound is given the common name, “Marshall'sacid”. The formula for Marshall's acid can be written in severaldifferent ways, including HO(O2)SO—OS(O2)OH, or H2S2O8. A structuraldrawing is shown in FIG. 1A. It is worth noting that Marshall's acid isfully symmetric, around the peroxide bond. If that bond is broken, tworadicals will be released, and they will NOT be normal and conventionalmolecules of sulfuric acid; instead, each will be an extremely unstable,aggressive, and corrosive radical version of sulfuric acid. Each such“sulfuric acid radical” will be strong enough to rip away a hydrogenatom (i.e., both proton and electron) from methane (CH4), to create anormal and conventional molecule of sulfuric acid, and a methyl radical.Therefore, a single molecule of Marshall's acid, if mixed with methane,will create two molecules of stabilized sulfuric acid, and two methylradicals. If SO3 is also present in the mixture, each methyl radicalwill attach itself to a molecule of SO3, thereby creating a radicalversion of MSA. Each MSA radical will have the right amount of strengthto then attack another molecule of fresh methane, thereby sustaining (or“propagating”) the chain reaction.

Accordingly, Marshall's acid was synthesized and used as the radicalinitiator compound, in the first laboratory tests which were shown toinitiate the methane-to-MSA chain reaction, exactly as predicted by asophisticated computer simulation that had already been run by theApplicant, before the first benchtop tests were carried out.

As a brief historical note, the details and results of that computersimulation were then given to Dr. Ayusman Sen, chairman (at the time) ofthe Penn State University Chemistry Department, which was paid by theApplicant to perform those benchtop tests. Even though the computersimulation had already predicted (accurately) exactly what would happen,Dr. Sen later claimed (fraudulently, in the opinion of the Applicant)that no one could have predicted the outcome, and therefore, he and hisassistant were the true inventors of the process. His claim led toissuance of U.S. Pat. No. 7,119,226, which deserves close and carefulattention by anyone interested in the history of science, or in thehistory of Penn State University (which also was suffering from othermajor problems at that time, which led to criminal indictments andconvictions of its President and a number of other officials) duringthat period of time.

Returning to the chemistry itself, Marshall's acid has several problems;among other things, it is difficult to make and handle, since it isaggressively unstable and will break down substantially within less thana day under most types of normal storage conditions. Therefore, theApplicant herein began considering and studying various alternateinitiators, after the methane-to-MSA chain reaction had been shown towork, when initiated with Marshall's acid. One of the more promisinginitiators he initially settled upon was a di-methyl variant ofMarshall's acid, which has the chemical name di-methyl sulfonyl peroxide(DMSP). It can be made in a relatively simple and straightforwardmanner, by passing MSA through an electrolysis unit, which will operatein a manner described in more detail below under the heading,“ELECTROLYSIS, AND MIXTURES OF PRIMARY INITIATORS.” Very briefly, whenMSA (an acid) dissociates into ionic form, the negatively-chargedanions, H3C—S(O2)O⁻, will be attracted to the positively-chargedelectrode submerged in the liquid MSA. Driven by a strong voltage, theelectrode will remove an electron from each anion, to convert each anioninto a radical. Two such radicals will bond to each other, in a mannerwhich forms a peroxide bond (i.e., a double-oxygen bond, as mentionedabove) in the center of a symmetric molecule. The resulting moleculewill be identical to Marshall's acid, except with two methyl groupsattached to it (one at each end). That molecule is called di-methylsulfonyl peroxide (DMSP). As described above, it is simple to make, fromMSA, using simple electrolysis, and it is more stable, and easier tostore and handle, than unmodified Marshall's acid.

In addition, when its peroxide bond is broken apart, DMSP will releasetwo MSA radicals, and each of those radicals has enough strength toextract a hydrogen atom from methane, thereby: (i) converting each ofthe two MSA radicals into stabilized MSA; and, (ii) creating two moremethyl radicals, which will then attach themselves to SO3, in a mannerthat creates more MSA radicals, in a manner which helps sustain thechain reaction.

Accordingly, if DMSP is used as the initiator to commence the chainreaction, the two MSA radicals that are released from the DMSP peroxidewill become part of the exact same chain reaction that converts methaneinto MSA. The DMSP initiator will create more MSA (i.e., the desiredproduct of the reaction), rather than creating sulfuric acid, as occurswhen unmodified Marshall's acid is used to initiate the radical chainreaction.

Therefore, DMSP is regarded as a preferred initiator for convertingmethane into MSA, and its use for that purpose was described in otherprior patent applications by the same Applicant herein.

Another peroxide that deserves mention is usually referred to by thecommon name, Caro's acid. Its chemical name is peroxy-monosulfuric acid,and its formula can be written as HO—S(O2)-O—OH. It was initiallyregarded as significant, in the methane-to-MSA reaction pathway, mainlybecause it is an intermediate that is formed during the synthesis ofMarshall's acid. As described in U.S. Pat. No. 3,927,189 (Jayawant1975), hydrogen peroxide (HOOH) can be reacted with SO3 to form Caro'sacid, and if additional SO3 is added to the Caro's acid, at least someof it will convert into Marshall's acid. Accordingly, in the initialreport of the tests that described the use of Marshall's acid toinitiate the chain reaction which converts methane into MSA, containedin Example 2 of U.S. Pat. No. 7,282,603 (Richards 2007), several of thepreparations of Marshall's acid were explicitly described as alsocontaining some quantity of Caro's acid (including 7.8% Caro's acid inRun 2, and 19.2% Caro's acid in Run 4). Neither of those mentions wereregarded as important, at that time, since: (1) the sulfuric acidradical that is released by Caro's acid, when its peroxide bond isbroken, is exactly the same as the two sulfuric acid radicals that arereleased when the peroxide bond of Marshall's acid is broken; and, (2)the hydroxy radical that also is released, when the peroxide bond ofCaro's acid is broken, is simply too weak (by itself) to extract ahydrogen atom from methane, to convert the methane into a methylradical.

It was not until years later—after additional research indicated thatSO2 might be an important chain-terminator in the methane-to-MSA chainreaction—that Caro's acid moved back into active consideration as acandidate initiator. A discussion of that sequence of events is not partof this Background section, since it became part of this invention.

Accordingly, one object of this invention is to disclose means andmethods for preventing or minimizing the formation of chain-terminatingmolecules, and/or for quenching and inactivating such chain-terminatingmolecules if and when they are created, inside a reactor vessel which isusing a radical chain reaction to bond methane to SO3 in a manner whichproduces methane-sulfonic acid (MSA).

Another object of this invention is to disclose means and methods forabsorbing, neutralizing, inactivating, quenching (or otherwise reducing,eliminating, minimizing, controlling, or similar terms)chain-terminating molecules, after they have been created inside areactor vessel which is using a radical chain reaction to convertmethane into MSA.

Another object of this invention is to disclose means and methods foravoiding and/or minimizing the presence and concentration of any SO2(sulfur DI-oxide) molecules, inside a reactor vessel which is using aradical chain reaction to convert methane into MSA.

Another object of this invention is to disclose means and methods forrunning a radical chain reaction which bonds methane to SO3, in a mannerwhich produces MSA, in a more efficient and profitable manner, withhigher yields and selectivity, and with fewer unwanted byproducts and/orwaste products.

Another object of this invention is to disclose a tube reactor systemwhich contains passive (or inert, static, etc.) mixing devices, andwhich enables “plug flow” through the tube(s) and minimizes anybackflow, thereby carrying any chain-terminating molecules out of thereactor, to minimize their ability to interfere with the chain reaction.

Another object of this invention is to disclose means and methods forrunning a radical chain reaction which bonds methane to SO3 to form MSA,which uses MSA as the solvent.

These and other objects of this invention will become more apparent fromthe following summary, description, and drawings.

SUMMARY OF THE INVENTION

Improved initiators, solvents, and SO3 mixtures are disclosed herein,which can increase the yields and efficiency of a chemical manufacturingprocess which uses a radical chain reaction to convert methane (CH4),which is a gas under any normal conditions, into methane-sulfonic acid(MSA), a liquid. MSA is useful and valuable in its own right, and italso can be processed to create desulfured fuels and other valuablechemicals.

With regard to improved initiators, a preferred type of initiatorcombination has been identified, comprising at least two differentperoxide sulfate compounds, which will exert overlapping but differentroles. One type or class of initiator can be regarded and referred to asa “primary” (or major, main, principle, dominant, or similar terms)initiator, and the other type or class of initiator can be can beregarded as an “extender” (or secondary, supplemental, enhancing,tuning, tweaking, or similar terms) initiator.

The “primary” initiator(s) will be primarily responsible for initiatingthe “radical chain reaction” described herein, which will bond methane(CH4) to sulfur trioxide (SO3) in a consistent manner which generatesmethane-sulfonic acid (MSA) at purity levels which, in tests run todate, have exceeded 95%, and sometimes 98%. Any of several “primary”initiators (or mixtures of “primary” initiators) can be used, including:

1. an unmethylated, symmetric, di-sulfuric peroxide compound calledMarshall's acid, as described above and illustrated in FIG. 1, which hastwo sulfuric acid groups bonded to each other through a double-oxygenperoxide linkage;

2. methyl-sulfonyl-peroxo-sulfuric acid (the acronym is MSPSA). Thiscompound also can be called methyl-Marshall's acid (semi-abbreviated asmeMarshall's acid, or as mMarshall's acid), since it is a molecule ofMarshall's acid with a single methyl group bonded to one end. Toemphasize that it is non-symmetric, and has only a single methyl groupat one end, and to distinguish it from a di-methyl variant which also isimportant, it also can be called mono-methyl-Marshall's acid; and,

3. di-methyl-sulfonyl-peroxide (the acronym is DMSP), which also can becalled di-methyl-Marshall's acid, since it is a molecule of Marshall'sacid with two methyl groups (i.e., with a methyl group coupled to eachof the two sulfate groups).

Both of the methylated compounds listed above are more stable, andeasier to handle and work with, than unmethylated Marshall's acid.Furthermore, one of the radicals released by the mono-methyl variant,and both of the radicals released by the di-methyl variant, willgenerate MSA, after the peroxide bond is broken to release thechain-initiating radicals; by contrast both of the radicals released bynon-methylated (i.e., normal) Marshall's acid will generate sulfuricacid, rather than MSA. As a result, the methylated variants are likelyto be preferred, over non-methylated Marshall's acid, at most MSAmanufacturing sites.

An “extender” initiator also can be added to the reaction mixture, to“quench” (or neutralize, remove, eliminate, re-activate, or similarterms) one or more types of “chain terminating” molecules (chemistsoften call such molecules “species”) that may have arisen or accumulatedinside an MSA-forming reactor. If not “quenched” and removed from thereactor, such molecular species can seriously and in some cases severelyreduce the yields (and efficiency, profitability, and desirability) ofthe radical chain reaction which converts methane into MSA.

The most notable and apparently important “chain terminating species”that has been seen in the tests done to date is sulfur DI-oxide (SO2).It can be oxidized back up to SO3 (i.e., sulfur TRI-oxide, which is auseful and valuable reagent in the radical chain reaction which makesMSA) by using methyl-Caro's acid as an “extender” initiator, asdescribed in more detail below.

Since the “extender” initiator will be added to the reaction mixture insubstantially smaller quantities than the “primary” initiator(s), it canbe injected into the reactor, or generated within the reactor: (i)either continuously, or intermittently; and, (ii) either mixed inadvance with the “primary” initiator, or via a separate injector system.

It also is disclosed herein that a mixture of SO3 in MSA (using the MSAas a solvent) appears to offer certain advantages over mixtures of SO3in sulfuric acid, when used in the reactions disclosed herein. Sincemixtures of SO3 in sulfuric acid have been referred to for decades bythe term “oleum”, the new mixtures of SO3 in methane-sulfonic acid arereferred to herein by a non-trademarked generic phrase, which is“SO3/MSA”. That mixture also is referred to by a newly-coined word,METHOLEUM™. Trademark registration is being sought for that term.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 contains panels 1A and 1B on the same sheet, so that they can bedirectly compared against each other.

PANEL 1A depicts the synthesis of standard Caro's acid, by mixinghydrogen peroxide (H₂O₂) with sulfur trioxide (SO3) and/or sulfuric acid(H2SO4). If more SO3 is added, it will drive the conversion of Caro'sacid into Marshall's acid, with an equilibrium balance that stronglyfavors Marshall's acid. Therefore, the ratio of Marshall's acid andCaro's acid, in a mixture that contains both, can be controlled bylimiting the quantity of SO3 that is added to the preparation.

PANEL 1B depicts the synthesis of the mono-methyl variants of bothCaro's acid, and Marshall's acid. Rather than mixing hydrogen peroxide(H₂O₂) with sulfur trioxide (SO3), the H2O2 is mixed instead withmethane-sulfonic acid (MSA), which effectively carries a methyl groupbonded to the sulfur atom of an SO3 group. Subsequently, if additionalSO3 is added to the mixture, it will drive the “methylCaro's acid”(i.e., methyl-sulfonyl-peroxy-acid, abbreviated as MSPA) toward“methyl-Marshall's acid” (i.e., methyl-sulfonyl-peroxo-sulfuric acid,abbreviated as MSPSA). Therefore, to create a controlled mixture whichis mainly MSPSA (i.e., meMarshall's acid) with a small quantity of MSPA(i.e., meCaro's acid), the quantity of SO3 which is added to themsCaro's acid is limited to slightly less than a molar equivalent of thequantity of MSPA.

FIG. 2 is a schematic drawing of an integrated processing system formanufacturing MSA from methane, which uses sulfuric acid as a primarysolvent for both SO3 (in the same manner as the mixture called “oleum”within the chemical industry), and MSA. This drawing is included hereinto help explain a “continuous acid loop” system which uses and includesboth:

(i) a “rich acid” stream containing a high concentration of MSA insulfuric acid, passing from the MSA-forming reactor 110 to the MSAextracting unit 130; and,

(ii) a “spent acid” stream which contains only a small quantity of MSA,in sulfuric acid, which recycles that mixture from the MSA extractingunit 130, back to the MSA-forming reactor 110.

FIG. 3 is a schematic drawing of a different type of postulated/proposedprocessing system for manufacturing MSA from methane, which effectivelyeliminates sulfuric acid from the system (even though very small (trace)quantities may be formed, as unwanted byproducts), and which uses MSA,rather than sulfuric acid, as the solvent for each and both of: (i) SO3,the reagent which will combine with methane to form MSA; and, (ii)methane gas, which will be subjected to high pressures, to get it tocombine with the SO3. It is believed that, in at least some conditions,the processing system shown in FIG. 3 will be able to manufacture MSAwith a sufficient level of purity to eliminate any need for distillation(or other expensive extraction methods) to purify the MSA.

FIG. 4 depicts a first chemical pathway by which ozone can be used tohelp prepare sulfur-containing peroxide compounds which can function asinitiators for the methane-to-MSA radical chain reaction.

FIG. 5 depicts a second chemical pathway by which ozone can be used tohelp prepare sulfur-containing peroxide compounds which can function asinitiators for the methane-to-MSA radical chain reaction.

DETAILED DESCRIPTION

As summarized above, a combination of at least two different types ofinitiator compounds, comprising at least one “primary” initiator and atleast one “extender” initiator, are disclosed herein, which can be usedto activate, drive, and sustain a radical chain reaction which will bondmethane (CH4) to sulfur trioxide (SO3) in a manner which generatesmethane-sulfonic acid (MSA, H3C—SO3H). The MSA can be sold as is, or itcan be treated by “downstream” processing to separate the methyl groupfrom the sulfate group, to create desulfured compounds (such asmethanol, dimethyl ether, or other desulfured fuels or commoditychemicals). This will keep the recovered sulfates on-site, so they canbe recycled numerous times through the MSA-forming reactor, to make moreMSA.

The combination of “primary” and “extender” initiators, workingtogether, can make the reaction run more efficiently and economically.The “primary” initiator(s), which are specialized sulfur-containingperoxide compounds, can be broken apart by a suitable energy input (suchas UV light, a tuned laser beam, or heat), to release potent radicalswhich will quickly and efficiently convert methane, into methylradicals; and, the “extender” initiator (which can be mixed with theprimary initiator, or injected separately, either continuously, orintermittently) will eliminate “chain terminating” molecules (notablyincluding SO2) from the MSA-forming reactor, thereby increasing: (i) thenumber of cycles that the chain reaction can achieve, and (ii) thequantity of MSA which will be formed by the increased number of cyclesof the chain reaction.

Primary Initiators: Marshall's Acid and Methylated Derivatives

Based on experimental results, combined with insights into how variousmolecular and radical species function, it is asserted herein that anyof three related and similar compounds can function efficiently as a“primary” initiator, and the choice of which particular one to use (orwhat blend, combination or mixture of the three will be used), at anyspecific MSA manufacturing site, will depend mainly on the type ofsolvent system which is used at that site. As described below and asillustrated in FIGS. 2 and 3, either of two different types of solventsystems can be used, which are:

(1) a sulfuric acid solvent system, which will contain a “continuousacid loop” in which the MSA is mixed with sulfuric acid, at differentconcentrations in a “rich” acid stream (or leg), and a “spent” acidstream (which will contain a sharply reduced concentration of MSA afterpassing through an MSA extraction unit, such as a distillation column);or,

(2) an MSA solvent system, in which any sulfuric acid content is kept toa minimum (as an unwanted byproduct), and which uses MSA as the solventfor both the methane gas, and the SO3 reagent.

In ascending order of size and molecular weight, the three compoundswhich can serve as “primary” initiators are:

1. Marshall's acid, which in its non-methylated “conventional” form is adi-sulfuric acid peroxide with no methyl groups, as illustrated inFIG. 1. It has been known for decades, and it can be made by a two stepprocess, which involves: (i) mixing hydrogen peroxide (H2O2) with sulfurtrioxide (SO3), to initially form a compound called Caro's acid, whichhas the formula O3S—O—O—H, and (ii) reacting the Caro's acid withadditional SO3.

2. A mono-methyl derivative of Marshall's acid, which can be calledmethyl-Marshall's acid (or the shortened phrase meMarshalls acid). Thismono-methyl variant of a well-known di-sulfuric acid peroxide (i.e.,Marshall's acid) also can be called methyl-sulfonyl-peroxo-sulfuric acid(MSPSA). Its formula can be written as H3C—S(O2)-O—O—S(O2)OH, withdashes used to emphasize certain key bonds. It can be made by the stepsillustrated in FIG. 1B. It is believed and asserted to be a newcompound, first conceived and made by the Applicant herein, and it isclaimed as a new chemical compound. When methyl-Marshall's acid is splitinto two radicals, one of those radicals will form sulfuric acid, whenit removes a hydrogen atom from a methane molecule; the other radicalwill form MSA, which is the desired product of the radical chainreaction.

3. The di-methyl derivative of Marshall's acid, which can be calledeither di-methyl-Marshall's acid, or DMSP (the acronym fordi-methyl-sulfonyl-peroxide). Its formula can be written asH3C—S(O2)-O—O—S(O2)-CH3. It was previously disclosed by the Applicantherein, and as described in more detail below, it can be made by simplypassing MSA through a conventional electrolysis unit. When the DMSPperoxide subsequently is split into two radicals, both of those radicalswill form MSA (i.e., the desired product of the radical chain reaction)when they each remove a hydrogen atom from a methane molecule.

When compared to conventional (non-methylated) Marshall's acid, the twomethylated variants listed above are more stable, easier to handle, andless dangerous; and, the “less dangerous” trait is highly important,since these compounds will be in close proximity to methane, apotentially explosive gas, while it is being subjected to very highpressures. Accordingly, the methylated versions are regarded as beinggenerally preferred over conventional (non-methylated) Marshall's acid.

In addition to the “primary” initiator, a small quantity of an“extender” initiator also should be added to the MSA-forming reactionmixture, in order to “quench” and eliminate chain-terminating molecules,such as SO2. The best such agent discovered to date for that use is acompound called methyl-sulfonyl-peroxy-acid (abbreviated as MSPA), withthe formula H3C—S(O2)-O—OH. It also can be called methyl-Caro's acid (orthe shortened phrases, meCaro's or mCaro's acid), since it is amono-methyl variant of a compound called Caro's acid. It can be made bymethods disclosed below, in the Examples and in the drawings.

Only a relatively small quantity of the MSPA (i.e., meCaro's acid)“extender initiator” should be used, compared to the “primary”initiator(s). The optimal ratio of the initiators is likely to vary,among different production sites, based on the grade and purity of (andthe specific types and amounts of impurities in) the methane and SO3that are being processed at that site. Unless and until specific dataindicate otherwise, quantities of MSPA for initial optimization testingat any specific MSA manufacturing site generally should range from about2 to 10% of total initiator weight. The MSPA can be added to the primaryinitiator, so that both of them will enter the MSA-forming reactortogether. Alternately, the MSPA can be injected separately, eithercontinuously or intermittently.

Since large systems that will handle large volumes of methane can bemore complex and expensive than smaller systems (which can includetruck-mounted, “skid-mounted”, or similar portable systems), apresumption arises that, in large systems, any MSPA should be injectedseparately from the “primary” initiator(s), so that if any problemsarise, and when periodic or other maintenance is required, the overallMSA processing system will suffer only minimal disruptions.

In addition, due to the very high corrosiveness of all of theabove-mentioned sulfuric peroxides, two or more independent initiatorinjector assemblies can be provided for any MSA-forming reactor, so thateither one can be detached from the unit and replaced, as a singleunitary subassembly, without having to shut down the MSA reactor andthen restart it and re-stabilize it again. This comment is not intendedto apply at all MSA production facilities; instead, it is anticipatedthat, once the process has been “proved out” in several commercialfacilities, additional work will commence, to design and create smalleroperating units that will focus on handling low methane output rates,with a range of methods and devices adapted for intermittent usage,minimal up-front costs, etc.

It also should be noted that any of the initiator compounds discussedherein can be injected either continuously or intermittently, tooptimize the balance of performance and economics at any particularsite. For example, at some sites, testing may indicate that a pulsedinjection of MSPA (as an “extender” initiator), once every 10, 30, or 60minutes, may be sufficient to handle low-level accumulations of SO2inside the reactor, while a “maintenance” quantity of one or more“primary” initiators is injected continuously.

As “primary” initiators, either or both of the mono- or di-methylvariants of Marshall's acid can potently activate the radical chainreaction. It initially was presumed and believed that the di-methylvariant, abbreviated as DMSP, was preferable to either Marshall's acidor (mono-methyl) meMarshall's acid, for two reasons: (i) DMSP can besynthesized relatively easily, merely by subjecting MSA to electrolysis;and, (ii) DMSP will not generate any sulfuric acid, and will simplycreate more MSA, when it is broken apart at its peroxide bond toactivate the initiator radicals.

However, the second factor will be insignificant at manufacturing siteswhich use sulfuric acid as a main solvent, as depicted in FIG. 2 and asdiscussed below.

Sulfuric Acid Solvent and “Continuous Acid Loop” Design

A better understanding of whether sulfuric acid, or MSA, should bechosen for use as the preferred solvent, at any specific MSAmanufacturing site, requires a grasp of how two overlapping and similaryet different processing systems can be designed and arranged, to alloweither solvent type to be used.

Fortunately, the similarities and overlaps between the two differenttypes of systems will allow either type of system to be built, and thenconverted to the other type of system, if operating results do not meetthe targeted levels, or if circumstances change (such as, for example,to incorporate any additional improvements which are made after thefirst few commercial-scale systems have been fully built, renderedoperational, and studied long enough for technicians and engineers tofigure out how to further improve them beyond the disclosures herein).

The first design that will be described herein is a “continuous acidloop” arrangement which uses sulfuric acid as the major solvent. It isschematically depicted in FIG. 2 herein, and it is described in moredetail in U.S. patent application Ser. No. 15/917,631, filed on Mar. 10,2018 by the same Applicant herein (the contents of that application areincorporated herein by reference, as though fully set forth herein).

It should be noted, at the outset, that this design arose largely fromthe Applicant's awareness of a long-standing industry practice, whichuses a mixture called “oleum” as a standard way to manufacture, store,transport, and handle SO3. In “oleum” mixtures, SO3 is mixed withconcentrated anhydrous sulfuric acid, for a number of reasons discussedin the Background section (which center on the fact that SO3 andsulfuric acid will form a dimer, usually called disulfuric acid orpyro-sulfuric acid, which has certain useful traits). With that industrypractice as a given, a baseline, and a starting point, the Applicantfigured out how to weave conventional “oleum” preparations into a designfor an integrated processing system. Rather than trying to get rid ofthe sulfuric acid, he figured out how to tolerate it, and use it as adesign constraint.

To explain various points worth noting about the “continuous acid loop”design as depicted in FIG. 2:

1. As indicated by the arrows from the left, fresh methane (which can bepassed through any desired type of purification, drying, or otherpreparation and pumping/compressing unit 102), fresh SO3 (in an oleummixture, as mentioned above), and a small quantity of “radicalinitiators” (i.e., the types of sulfur-containing peroxide compoundsdescribed above) are all injected, at high pressure, into MSA-formingreactor 110. Inside that reactor, the radical chain reaction discoveredby the Applicant herein causes the methane and SO3 to bond together, ina consistent manner which generates MSA at a high level of purity.

2. To optimize and maximize the overall daily and yearly tonnage of MSAthat can be manufactured by a plant having any specific size, thereaction mixture is pumped through the MSA-forming reactor at a ratewhich leads to a moderately high but incomplete level of reactioncompletion. The reaction itself is “asymptotic”; like an “asymptotic”mathematical curve on a graph, which will keep getting closer and closerto some value without ever actually reaching that value, the MSA-formingchain reaction can approach a 100% level of completion, but it can neverreach a level of total 100% completion, since “the last lonelymolecules” of unreacted methane and SO3 will become so sparse, andscarce, that their likelihood of contacting each other—so that they canreact with each other to form MSA—will drop to extremely low levels.

As a result, the best, most practical, most profitable operations can beachieved by allowing enough “dwell time”, inside the reactor, fornewly-arrived reagents to react only up to a completion level that islikely to be somewhere between about 50 and about 80 percent. Thatincomplete reaction mixture will then be removed from the MS A-formingreactor 110, and—crucially—it is then passed through a processing unit120, which can be called an evaporator, a stripper (or stripping unit),or similar terms. That unit 120 will pull out (or “strip out”) unreactedmethane and SO3 molecules, so that they can be repeatedlyreturned/recycled back into the MSA-forming reactor 110, to supplementthe additional fresh reagents which will also will continue to be pumpedinto the MSA-forming reactor 110. An additional processing unit 210,which can be called a gas condenser, an SO3 recovery unit, or similarterms, can also be included in any such system, if it is desired toseparate the methane recycle stream from the SO3 recycle stream (suchas, for example, to improve the efficiency of any additionalpurification, temperature adjustments, or other processing of eitherrecycle stream, or to enable independent controls over the rates atwhich both recycled reagents are pumped back into the MSA-formingreactor).

Accordingly, allowing the MSA-forming reaction to proceed to only apartial (but optimized) level of completion, and returning unreactedreagents back into the reactor on a continuous basis, will allow thesystem as a whole to create a larger MSA output, over any span of time,than could be achieved if the “throughput” rate of the MSA-formingreactor 110 were slowed down, in a misguided effort to reach a high (butnon-optimal) level of completion during any single “pass” through thereactor.

3. A “rich acid” mixture of MSA (at high concentration) and sulfuricacid will emerge from the “stripping unit” 120 after the unreactedmethane and SO3 have been removed.

4. The “rich acid” mixture will be passed through an MSA extraction unit130, such as a distillation column. That unit will be run underconditions (involving temperature, pressure, number and spacing ofcondensation trays, etc.) which will allow a relatively pure stream ofMSA to be removed from the system, suited for sale, on-site usage,additional purification (or “polishing”, etc.) if extra-high purity isneeded, etc.

5. Since most of the MSA will be removed from the “rich acid” stream byextraction unit 130, the residual stream which emerges from unit 130will contain mostly sulfuric acid, and is called a “spent acid” stream.However, some quantity of MSA will still be present in that “spent acid”stream, because the methyl domain of MSA can help methane gas dissolvemore rapidly and efficiently into a liquid containing at least some MSA.

6. The “spent acid” stream which emerges from extraction unit 130 can bepurified or processed, in any way desired and appropriate, in device140. It is then recycled/returned back into the MSA-forming reactor 110.

7. A small portion of the relatively pure MSA stream which emerges fromextraction unit 130 can be passed through an electrolysis unit, tocreate the dimethyl peroxide compound called DMSP (also calleddimethyl-Marshall's acid). As described above, DMSP can be used as a“primary” initiator to help sustain the radical chain reaction whichcreates more MSA.

8. Alternately, a controlled quantity of relatively pure MSA can bemixed with a controlled quantity of the “spent acid stream”, to create amixture having any desired ratio of MSA and sulfuric acid. If that acidmixture is treated by electrolysis, the resulting peroxides will containa combination of unmethylated Marshall's acid, mono-methyl-Marshall'sacid, and di-methyl-Marshall's acid, in fractions which will depend onthe concentrations of the MSA and sulfuric acid entering the unit. Eachand all of those three compounds can function as an efficient “primaryinitiator” for the radical chain reaction. A range of peroxide mixtureshaving different fractions of those three candidate agents can be testedat any MSA manufacturing site, to determine which particular blend orbalance of those three compounds will perform best, at that particularsite.

MSA as Both the Product, and the Solvent

After pondering (for some time) the results of one of the continuousflow processing tests that were performed by a contract laboratory(which was selected and hired by the Applicant to do additional benchtoptesting, to generate impartial and objective data which could beevaluated both by him, and by a potential licensee company, duringlicensing negotiations), the Applicant has come to believe that analternate pathway may be more effective than using sulfuric acid and“oleum” to keep SO3 in its desired “gamma” form.

One of those continuous flow tests, which is described in Example 5,directly compared two different solvent systems against each other,under identical conditions. The two solvent systems tested were:

(1) SO3, in sulfuric acid (i.e., conventional “oleum”); and,

(2) SO3, in MSA as a solvent.

That test was not performed until after numerous other tests had alreadybeen completed, and the prior tests were used to select consistentgood-performing conditions (including temperature, pressure, poweredversus passive mixing, etc.) which could then be used during directcomparison tests of other parameters (such as different solvents,different concentrations of SO3 in a solvent, etc.).

As stated in Example 5, the percentage of SO3 conversion, when MSAformation rates were tested using MSA as the solvent, was better thanthe percentage of SO3 conversion, when tested in sulfuric acid as thesolvent.

That test result, if considered in isolation, is only a single datapoint, and it is not sufficient to establish a range of conditions underwhich MSA, as the solvent for SO3, can outperform sulfuric acid, thestandard and conventional solvent for SO3 in commercially availableoleum. However, even as only a single data point, it points toward MSAhaving at least some advantages over sulfuric acid, as the solvent for amethane-to-MSA conversion process. This becomes even more true, andpotentially valuable, when it is also noted that—as pointed outpreviously by the same Applicant herein—the methyl domain of MSA canhelp pressurized methane dissolve more rapidly into a liquid solution.

Accordingly, FIG. 3 is a schematic depiction which shows the arrangementof the main processing components of an MSA manufacturing system whichuses MSA as the solvent, and which restricts sulfuric acid to only verysmall quantities (created as undesired byproducts of the MSA-formingreactions). The methane preparation unit 102, the MSA-forming reactor110, the evaporating/stripping unit 120 for removing unreacted SO3 andCH4, and the processing unit 210 for separating unreacted SO3 fromunreacted CH4 so that they can be processed as necessary and sent backinto the MSA-forming reactor 110, will all be essentially the same as inthe sulfuric acid solvent system shown in FIG. 2. That high degree ofoverlap ensures that, if a “continuous acid loop” system which usessulfuric acid is built and then debugged, it will be relativelyinexpensive and straight-forward to use nearly all of its components totest the performance of the same system, if it is converted over to MSArather than sulfuric acid as the main solvent.

As indicated by FIG. 3, instead of having to pass a “rich acid” stream(i.e., a high content of MSA, in a lesser quantity of sulfuric acid),which emerges from evaporator (or stripper) 120 through a distillationunit or other MSA extractor which will require a large amount of energyinput, the MSA stream which emerges from unit 120 is likely to alreadyhave enough purity to render it fully suited for at least some types ofuses, including uses which only require “rough grade” purity (such asmetal ore processing, or metal recycling; by contrast, uses such ascleaning or etching metal surfaces, during the manufacture of integratedcircuits, require much higher levels of purity).

As also shown in FIG. 3, a portion of the MSA output stream whichemerges from SO3/CH4 remover 120 can be diverted, for recycling backthrough the MSA-forming reactor 110. That recycled stream can be passedthrough a purification unit 140 if desired, and a portion also can bepassed through an electrolysis unit, to convert it into DMSP (asdescribed above, DMSP is the acronym for di-methyl-sulfonyl peroxide,the di-methyl variant of Marshall's acid).

As a final comment, it also should be noted that the SO3 reagent whichis pumped into the MSA-forming reactor 110 (as shown by two differentarrows, with the arrow at the lower left corner of reactor 110representing fresh SO3 reagent, and the arrow at its upper right cornerrepresenting recycled SO3) can be suspended in MSA as a solvent, ratherthan sulfuric acid. The first batches of “fresh SO3 reagent, in MSAsolvent” mixture will need to be obtained from SO3 suppliers by means ofcustom orders with detailed specifications, since it is not currentlyavailable.

Because of its similarity to “oleum”, the standard chemical name formixtures of SO3 in sulfuric acid, the Applicant herein has applied fortrademark registration rights for the name METHOLEUM as a trademark.Trademark protection can be used to help ensure that any such products,offered by any supplier with a proper license, will have sufficientpurity and quality to enable and sustain a methane-to-MSA conversionprocess using the radical chain reaction discovered by the Applicant.

To avoid risks of confusion, trademarked names generally should be usedas adjectives to identify a qualified supplier of a product or service,rather than as a noun to identify the product itself. Therefore, thegeneral name used herein for preparations of SO3 as a reagent, suspendedin MSA as a solvent, is “SO3/MSA”. That phrase can be modified by aadding a percentage number to the SO3 (such as SO3-35/MSA, or“SO3(35)/MSA”, to indicate the weight percentage of the mixture whichwill be contributed by the SO3 component.

This is not the first time that SO3 has ever been mixed with MSA;Robinson 1966 described various tests results that arose when variousconcentrations of SO3 were dissolved in MSA. That article focused onshifts in certain types of analytical peaks that occurred when themixtures were analyzed by (i) nuclear magnetic resonance (NMR), and (ii)Raman spectroscopy. However, there apparently were no proposals, in thatarticle, that such mixtures might be useful for any type of industrialor other commercial operations of products.

Electrolysis, and Mixtures of Primary Initiators

The process called electrolysis can be used to create, on-site, theperoxide compounds which will initiate the radical chain reaction. Forthose who are not already familiar with electrolysis, its ability tocreate peroxide condensates can be explained by using methane-sulfonicacid as an example. This same type of process will work with any acidwhere a hydrogen proton leaves an oxygen atom (including sulfuric acid,and nearly all organic acids).

To carry out the type of electrolysis that will generate peroxidecompounds, two electrodes (or, two sets of electrodes, such as a “stack”of parallel metallic plates having alternating positive and negativecharges, spaced slightly apart from each other so that a liquid willflow through the gaps between the plates are submerged in a liquidsolution of an acid, such as MSA.

A strong voltage is imposed across the two electrodes (or across thepaired sets of electrodes, if a “stack” is used) that have beensubmerged in the acid. Most industrial-grade electrolytic units useelectric transformers to boost the “input voltage” (such as conventional110-volt current, from any standard wall outlet) to a higher voltagelevel (200 to 500 volt levels are common, and voltages greater than 1000volts can be created, using either a 110 or 220 volt supply, ifdesired). Devices called “rectifiers” also are used, to convertalternating current (AC) voltage into a “direct current” (DC) voltage,which always pushes electrons in a single consistent direction (similarto battery power, but with much higher voltages than are normal forbatteries).

The resulting powerful DC voltage will cause one electrode (called the“anode”) to have a positive charge, which will attract anions (i.e.,negatively-charged ions) which have been released by the acid. The otherelectrode (the “cathode”) will have a negative charge, which willattract cations (i.e., positively-charged ions, which will be H⁺hydrogen ions when acids are involved.

The electrodes used in electrolysis can have any desired shapes. Inlaboratory settings, they often are rod-like devices, which can held inposition by simple clamps. In industrial operations, they more commonlyare provided by flat parallel plates, configured as a series or “stack”of multiple parallel plates, positioned so that positively andnegatively charges plates alternate with each other, within the stack.Chemical-resistant ceramic or polymer inserts are used to hold theplates apart and maintain proper spacing between them; these insertspush back against the electrical attraction that is generated betweenadjacent plates having opposite charges.

Since MSA is an acid, some of the molecules in the acid will naturallyand spontaneously dissociate, in a way that releases H⁺ (hydrogen)cations and H3CSO3⁻ (methyl sulfate) anions. When a strong voltage isimposed on liquid MSA by electrodes submerged in the liquid, thehydrogen cations will be attracted to the negatively-charged cathode,while the methyl sulfate anions will be attracted to thepositively-charged anode.

As the hydrogen cations in the liquid gather around the cathode, theyare provided with electrons, by the electrical current that is being“pushed” into the liquid by the cathode. An electron that emerges fromthe anode will initially convert a H⁺ cation into a H* radical (theasterisk indicates an unpaired electron). These radicals are unstable,and two H* radicals will bond to each other. This creates hydrogen gas,H2, which will rise to the surface as bubbles in the liquid. Whenever asubstantial quantity of hydrogen gas is formed (which will occur in anyindustrial-sized units), gas collectors must be used, to handle andremove the hydrogen bubbles safely, since hydrogen gas can becomeexplosive if it accumulates in any localized area.

At the same time, negatively-charged H3CS(O2)O⁻ (methyl sulfate) anionswill gather around the positively-charged anode surfaces. These MSAanions will surrender an electron to the anode (thereby completing acircuit, and establishing an electrical current through the liquid,driven by the voltage that is being imposed on the electrodes and theliquid). When an MSA anion loses an electron, it becomes an MSA radical.Since the unpaired electron is on one of the oxygen atoms bonded to thesulfur, these MSA radicals can be called methyl-sulfonyl-oxyl radicals.

These types of radicals are highly reactive, and they will be drawn,gathered, and clustered close together, by the positive electricalcharge on the surface of the anode. When they bump into each other, twooxygen radicals will form a peroxide bond, in a manner which is theexact opposite of what happens when a peroxide bond is broken apart byUV light, a laser beam, or heat.

Accordingly, if two H3CS(O2)O— ions (spontaneously released by MSA, inan acid bath) are converted into H3CS(O2)O* radicals by a voltage-drivencurrent in an electrolysis unit, those two radicals will bond together,in a manner which forms a peroxide bond. The resulting compound can becalled di-methyl-sulfonyl peroxide (DMSP); and, as mentioned above, italso can be called di-methyl-Marshall's acid, since it is a variant ofMarshall's acid which contains two methyl groups.

This method of creating DMSP, by electrolysis of MSA, has been known fordecades. It is described in U.S. Pat. No. 2,619,507, invented by G. D.Jones and R. E. Friedrich, entitled “Di(methane-sulfonyl) peroxide andits preparation”, issued Nov. 25, 1952, assigned to Dow Chemicals. TheDMSP created by that method was used for purposes unrelated to thiscurrent invention; in specific, U.S. Pat. No. 2,619,507 described itsuse for catalyzing the polymerization of vinylidene chloride. Inaddition, U.S. Pat. No. 4,680,095 (Wheaton 1987, assigned to PennwaltCorp.) provides additional information on electrolytic methods forsynthesizing DMSP, and U.S. Pat. No. 4,910,335 (Wheaton et al, U.S. Pat.No. 4,910,335) describes methods for using DMSP to improve the clarity,coloring, and purity of various types of sulfonic acid derivatives(including MSA).

Under the laboratory-scale conditions that were described in U.S. Pat.No. 2,619,507, DMSP was collected from the anode surfaces as awater-insoluble white powder, which apparently was scraped off of thecathode surface after the cathode had been removed from the electrolysisbath and allowed to dry. Under the different conditions described inU.S. Pat. No. 4,680,095, the solution containing the DMSP was removedfrom the electrolytic cell, and chilled until the peroxide productprecipitated out of solution.

When scaled up to industrial operations, it likely will be possible todo any or all of the following:

(1) use one or more electrolytic anodes to create MSA radicals in theinlet of a reactor vessel that is creating MSA, in ways that will allowthe MSA radicals to directly contact and react with methane that is alsobeing pumped into the vessel, thereby completely avoiding the need to gothrough DMSP peroxide as an intermediate;

(2) collect DMSP in liquid form, as a compound that is dissolved in MSA(or a mixture of MSA and sulfuric acid) as a carrier or solvent; or,

(3) collect DMSP in solid form, as a residue that can be scraped off orotherwise removed from anode surfaces, using a harvesting or gatheringoperation that may involve, for example:

(i) a procedure which involves chilling the electrolyzed liquid(containing DMSP dissolved in MSA) to a temperature that will cause theDMSP to precipitate out of solution, in a way that allows simplifiedharvesting of the solidified DMSP; or,

(ii) temporarily stopping the electrolysis, raising the anode surfacesout of the solution, and physically wiping solidified DMSP material offof one or more anode surfaces, using an automated roller, spatula,squeegee, or similar system.

If storage, transport, or other handling of the DMSP is desired at anyspecific site, the solid, semi-solid, or liquid form that the DMSP willtake during those steps will depend on factors that can be controlled,including: (i) the temperature(s) used for storage and transport, and(ii) the presence or absence and the concentration of MSA or any othercarrier, solvent, stabilizer, or other additive that may be present, inthe DMSP preparation. Such factors are governed by costs and economics,which vary between differing locations and operating environments,rather than by technical limitations or obstacles.

Additional information on the creation and spectroscopic analysis of MSAradicals is available in sources such as Korth et al 1990, whichreported that when “laser flash photolysis” was used to create MSAradicals, their typical lifetimes ranged from 7 to 20 microseconds, inthe solutions that were used. It must be emphasized that those averagelifetimes were based on specific operation conditions and mixtures; inindustrial operations as described herein, other pathways and reactionparameters can be developed as suggested above (such as by passing MSAdirectly across electrolytic anodes that are located in one or moreinlets of an MSA-producing reactor), which will promote the directcontact and reaction of MSA radicals with methane gas, thereby avoidingthe necessity of having to pass through DMSP intermediates that mustthen be cleaved, to release MSA radicals, before the radicals can reactwith methane.

Another point needs to be made about the use of electrolysis to form“peroxide dimers”. If 50% MSA and 50% sulfuric acid are mixed togetherand passed through an electrolysis unit, they will create a mixture ofperoxide dimers. For simplicity, if one assumes that “Acid A” and “AcidB” are mixed together (and have roughly comparable dissociation rates),and are passed through an electrolysis unit which converts the anionsreleased by both acids into peroxide dimers, that process will create amixture of roughly 25% AA, roughly 25% AB, roughly 25% BA, and roughly25% BB. Since AB and BA are exactly the same molecule (either one can be“formed” by simply flipping the other one, end-to-end), that means thatthe resulting mixture will be about 25% AA, about 25% BB, and about 50%AB. Accordingly, if 50% MSA and 50% sulfuric acid are mixed together andpassed through an electrolysis unit, they will create about 25%Marshall's acid, about 50% methyl-Marshall's acid, and about 25%di-methyl-Marshall's acid (also called di-methyl-sulfonyl-peroxide,DMSP).

Caro's Acid and Methyl-Caro's Acid

Steps and reagents for making Caro's acid are well-known, and have beendescribed in detail in sources such as Example 4, in U.S. Pat. No.3,927,189 (Jayawant 1975). As indicated in FIG. 1A, which is the panelin the top half of FIG. 1, hydrogen peroxide (H₂O₂) is simply mixed withSO3 and/or sulfuric acid, at a suitable temperature and pressure. H2O2is readily available as a 70% solution in water, and mixtures of SO3 insulfuric acid are readily available in a form called “oleum”. Preferredtemperatures for this reaction generally are “mildly chilled, comparedto room temperature” range, such as about 15 to 20 degrees C. There isno need to carry out the reaction under elevated pressure.

Because the work in Jayawant '189 described laboratory tests thatrequired hours to complete, various methods and devices can and shouldbe used to speed up the reaction, for any industrial operations. Forexample, an active mixing device used to create these types of peroxidesis described in U.S. Pat. No. 5,304,360 (Lane et al). It used acombination of: (1) flow of a first reagent through an annular(cylindrical) ring, in a manner which created a moderately high speedspinning effect; (2) use of a slanted nozzle to spray the second reagentdirectly into the path of the spinning/oncoming first reagent, to creategreater impact speeds that encouraged reactions between the first andsecond reagent; and, (3) use of a center cooling pipe, to cool thereagents.

Other useful information on devices that can promote these types ofreactions can be gleaned by studying “static mixers”, which use baffles,orifices, helices, or other internal components that have beenpositioned inside a pipe or other flow conduit, to create higher levelsof mixing between two or more reagents as they flow through the conduit.Several good illustrations are provided in the Wikipedia entry on“Static Mixers”.

On the subject of equipment, it should be noted that Caro's acid andMarshall's acid are extremely corrosive compounds, when in dilute form,or when in the presence of water. There are some indications that ifthey can be maintained in anhydrous conditions, with no water availablefor additional interactions, they may be much less corrosive; and, itshould be noted that if a large excess of SO3 is present, it willeffectively sequester any water molecules, by converting them intosulfuric acid, therefore sustaining effectively anhydrous conditionswithin the types of reactant mixtures contemplated herein.

Accordingly, the types of mixtures described herein can be handled onlyin devices made of highly specialized corrosion-resistant alloys andcoatings. Anyone interested in specialty corrosion-resistant alloys canfind more information by searching for terms such as “Alloy 20”,“Stainless 316”, and various alloys sold under trademarks such asHASTALLOY, INCOLOY, STELLITE, and ULTIMET.

Comments herein about high pressures reflects the fact that the radicalchain reaction will be specifically designed and operated to force a gasto “collapse” and pass through a foam or emulsion stage as rapidly andefficiently as possible, to form a stable liquid that will remain liquideven after the pressure is reduced or removed. Accordingly, thepressures of interest herein, in methane-to-MSA reactors (which mustreceive any initiator compounds at the same high pressures describedherein) will necessarily be high. Since the total force exerted by anypressure inside a container is equal to a pressure multiplied by theinternal surface area of the container, smaller reactors can be operatedat higher pressure levels than larger reactors, while maintaining anappropriate “margin of safety”. Accordingly, operating pressures, insidea methane-to-MSA reactor, are likely to be in the ranges of:

(i) up to about 1500 pounds per square inch (psi, measured as “gaugepressure”, which uses local atmospheric pressure as a “baseline” valuewhich establishes a zero point), for relatively small orintermediate-sized reactors; and,

(ii) up to about 800 psi (and possibly higher), for larger reactors.

To partially purify Caro's acid (or methyl-Caro's, meMarshall's, orMarshall's acid, or DMPS), the mixture can be chilled as soon as it hasbeen formed. This will cause the Caro's (or methyl-Caro's, ormeMarshall's) acid to become a semi-solid waxy-type material, which canbe separated from water by any of several well-known types of devices,such as devices called “cooling crystallizers”, or by passing thewax-and-water mixture through a suitable type of screen, mesh, or gratewhich will allow the waxy material to cling to it while the water flowsthrough and is removed. The removal of water will be useful and helpfulin subsequent reaction steps, since water in the system will rapidlyconvert SO3 (i.e., an essential reagent) into sulfuric acid (which, evenif used as a solvent in an integrated system, is not as valuable asSO3).

If “standard” Caro's acid is going to be converted into “standard”Marshall's acid, as shown in FIG. 1A, it is done by adding SO3 to theCaro's acid. Detailed recipes for this reaction are contained in sourcessuch as U.S. Pat. No. 3,927,189 (Jayawant 1975) and U.S. Pat. No.5,304,360 (Lane et al).

To make methylCaro's acid (i.e., methyl-sulfonyl-peroxy-acid, or MSPA)instead of conventional Caro's acid, H2O2 is added to methane-sulfonicacid (H3C—SO3-H), instead of SO3. That makes good sense, since theperoxide will react most readily with the sulfate portion of themolecule, while the pendant methyl group will remain relativelyuninvolved and unaffected, attached to “the far side” of the sulfategroup. The same types of mildly-chilled reaction temperatures (and thespecialized mixing devices and methods) described above can be used.

To convert methylCaro's acid (i.e., MSPA) into methylMarshall's acid(i.e., methyl-sulfonyl-peroxo-sulfuric acid, MSPSA), SO3 is added. Thiscan be done under the same types of conditions described in U.S. Pat.No. 3,927,189 (Jayawant 1975), which performed exactly the samemolecular modification, by converting “standard” Caro's acid into“standard” Marshall's acid, while (once again) the pendant methyl groupwill remain generally uninvolved and unaffected, on the “far side” ofthe sulfur atom in the methylCaro's acid.

It also should be noted that, if used as an initiator mixture to triggerthe radical chain reaction in a methane-to-MSA reactor, it may not evenbe necessary to convert methylCaro's acid (i.e., MSPA) intomethylMarshall's acid (i.e., methyl-sulfonyl-peroxo-sulfuric acid,MSPSA), outside the reactor. The reason is that high concentrations ofSO3 will be directly present in any methane-to-MSA reactor, since SO3 isthe reagent which will create MSA when it becomes bonded to methane.

As a final comment on the subject of methylMarshall's acid, a section isincluded below, which discusses the potential for using ozone, as anoxidizing reagent that can help increase the conversion of methane gasinto MSA, and two chemical drawings are included herewith, showing twoalternate pathways that an ozone reagent might take, in such a process.Both of those two candidate pathways create and then consumemethylMarshall's acid, as an intermediate compound, and the bottomportion of both drawings shows the fate of the methylMarshall's acid. Asshown in both drawings, when its peroxide bond is broken, it willrelease both:

(i) one MSA radical, which has the proper strength to remove a hydrogenatom (both proton and electron) from a fresh methane molecule, therebycreating stable MSA and a new methyl radical, which will then combinewith SO3 to create another MSA radical, to keep the radical chainreaction going; and,

(ii) a sulfuric acid radical, which also has the proper strength toremove a hydrogen atom (both proton and electron) from a fresh methanemolecule, thereby creating both stable sulfuric acid and a new methylradical, which will then combine with SO3 to create another MSA radical,to keep the radical chain reaction going.

Accordingly, when methylMarshall's acid breaks apart, it will triggerthe formation of not just one but two methyl radicals, both of which caninitiate new chain reactions that can continue for multiple cycles,creating more MSA. And, as discussed below, since ozone is believedlikely to be capable of converting at least some quantity of sulfurtrioxide and MSA into methylMarshall's acid, ozone may be able toprovide a useful and efficient way to convert additional quantities ofmethane gas into MSA.

Continuous Flow Tests and Results

As part of the research which laid the necessary groundwork forconstruction of a full-scale pilot plant for making MSA from methane,the Applicant herein hired and paid an independent consulting firm toperform a number of tests, in ways which would generate objective andimpartial data which both he and a potential licensee company couldevaluate, analyze, and rely upon, during their licensing negotiations.That independent consulting firm specializes in benchtop testing, using“continuous flow” methods and equipment, of chemical reaction pathwaysthat have been shown to work in “batch reactor” settings. It is verycommon for any initial “reduction to practice” chemistry tests in alaboratory (also called “wet tests” or similar terms, to distinguishthem from computer simulations) to be done using batch reactor methodsand equipment. Accordingly, the challenges of “translating” andexpanding “batch” results, to the types of continuous-flow equipment andmethods which are used in most types of industrial manufacturing, canbenefit greatly from skilled assistance by experts who specialize“making that jump”. To use an analogy, “batch testing” is comparable totesting candidate drugs by contacting them with selected types of cellson a petri dish, while continuous flow testing is comparable to testingthose same drug candidates in living animals. Success at a first earlylevel is no guarantee of success at the next higher level.

The types of tests done by the consultants using continuous flowequipment and methods focused on factors such as flow rates, reactionkinetics, yields as a percentage of expensive reagents, quantities andtypes of unwanted byproducts, and other factors that will affect and inmany cases control the economic viability and profitability of aproposed new chemical process.

While the detailed results of such tests are not required to berevealed, to meet and satisfy the “disclosure of the best mode”requirements of the patent law, the requirement to disclose the bestmode of processing, in this particular situation, is believed to befully met and exceeded by disclosure of the points of information listedbelow.

As a final prefatory comment, in a number of comparative tests, only twotests were done, to evaluate the system's response to a specificvariable that was changed between the tests. As any good scientistknows, one cannot determine the shape of a curve by simply plotting twodata points on a graph, and then drawing a line between those twopoints. It may be that a relatively straight line which connects the twopoints will emerge, when additional data points are gathered, but it isalso entirely possible that a convex (hump-shaped) curve, or a concave(bowl-shaped) curve, or some other unexpected type of curve will emerge,as more testing is done.

Accordingly, one of the main goals, when performing only two tests oftwo different values, when evaluating the effects of some particularvariable or parameter on a chemical process, is to get a “ballpark”-typesense of whether a newly-developed system is “robust” and adaptable, andcan continue to function over a range of different operating conditions,or whether it is hyper-sensitive, delicate, and fragile, and poses risksof shutting down completely if even a single specific condition oroperating parameter is not maintained at a near-optimal level.

When evaluated by that standard, the radical chain reaction describedherein showed itself to be “robust”, adaptable, and able to convertmethane into MSA over a fairly wide range of changed conditions, in eachand all of the variables that were tested. That is a good and promisingcondition for any chemical reaction that is approaching scale-up andcommercialization, since it makes it much easier for operators at anyspecific site to tinker with, tweak, and test any operating variable orparameter they want to evaluate, to help them settle on a set ofbalanced and optimized operating conditions, using no more than routineexperimentation.

With that as a preface:

1. The tests used high-pressure gas-liquid conduits which used a“T”-shaped connector (with minimal internal volume) to combine a gasstream and a liquid stream, as follows:

(i) a gaseous stream, containing high-pressure methane gas, was pumpedinto the reactor system to establish the initial desired pressure; then,

(ii) a liquid stream flow was established, which contained oleum (i.e.,SO3 mixed with sulfuric acid; various different concentrations of SO3,in sulfuric acid, were tested), initiator, and MSA. It was injected intothe T-shaped connector, along with an ongoing supply of gas, and at thesame operating pressure.

2. Immediately after being brought together in the T-shaped connector,the gas-liquid mixture was passed through a porous type of disc,conventionally called a “frit”, which forms a permeable barrier at theentry to the reactor device. Frits having two different “average porediameters” were tested. One frit, made of woven strands of acorrosion-resistant metal alloy, had an average pore diameter of 40microns, while the other frit was made of a porous ceramic materialhaving an average pore diameter of 10 microns. The ceramic frit with thesmaller pores caused a substantially larger pressure drop (which willrequire higher pumping costs, when scaled up to commercial volumes);however, the increased yields of MSA under various processingconditions, when the ceramic frit was used to create smaller gas bubblesand increase the levels of mixing and contact surfaces between the gasand liquid phases, were substantial, and were deemed to be worth theextra pumping costs. Therefore, all subsequent testing used the ceramicfrits, for consistent and comparable results.

3. The reactor devices that were used for the tests were cylinders(called “bubble reactors”) made of stainless steel, with 15 ml internalvolumes (external diameter 9.5 mm, length 107 mm). Cylinders withextra-thick walls were used, to withstand the highest pressures theyencountered, with an extra margin of safety, due to the high risks ofdealing with inherently unstable sulfuric acid peroxides such asMarshall's and Caro's acids. Tests indicated that four cylinders,connected by tubing in sequence rather than in parallel (so that thegas-liquid mixture, which “collapsed” into a stable liquid as itconverted the methane gas bubbles into liquid MSA, had to pass throughall four cylinders) performed substantially better than 2 cylinders withthe same dimensions handling the same flow rates. However, increasingthe number of cylinders to 8 did not lead to a substantial additionalimprovement over 4 cylinders.

4. Testing also indicated that if baffle-type passive (or static) mixerdevices (as shown in websites such as koflo.com, sulzer.com, komax.com,chemineer.com, and statiflow.com) were included in the cylinders, toforce the methane and SO3 to change direction multiple times while underpressure as they flow through a bubble reactor, the outcomessubstantially improved, compared to cylinders which had no “baffles”inside them and which allowed the gas/liquid mixture to pass throughthem in a mode which is generally linear (or laminar) with minimalmixing. If a power-consuming active mixing device was included in thebubble reactors, the results were slightly but not substantially higherthan provided by the passive/static mixing baffles.

5. An additional point is worth noting, in relation to the use ofpassive/static/inert baffle-type devices to create adequate mixinginside tube reactors. The behavior of the tube reactors containing suchmixing devices, during actual conversion of methane and SO3 into MSA,indicated that a condition called “plug flow” was being achieved andsustained (or, very nearly approximated) by the liquid/gas mixtureflowing through the tubes. “Plug flow” is introduced and summarized inreadily available internet sources such as wikipedia.org/wiki/Plug_flow.In a chemical reaction as described herein, “plug flow” is highlydesirable, since it can help minimize or eliminate problems such as“backflow”, and zones of low activity or flow where unreacted reagentscan aggregate. In particular, by minimizing any backflow, “plug flow”can help eliminate the ability of chain-terminating species to remaininside the reactor, or to travel backwards into active reaction zonesinside the reactor; stated in other terms, plug flow can effectivelycarry any chain-terminating species out of a reactor, thereby minimizingtheir ability to interfere with and degrade the output of a chainreaction. Furthermore, it should be noted that “active” mixing devices(such as impellers, paddles, blades, or other actively-moving stirringor other devices which require power inputs, to drive their motion)would generally be assumed, by engineers and designers, to be necessary,in this type of reaction, to sustain rapid mixing and intimate contactof methane molecules with the other reagents which will convert themethane into MSA. Accordingly, the discovery that passive/static/inertbaffle-type devices, inside tube reactors, were sufficient to both (i)establish and sustain plug flow, and (ii) enable commercially viable andprofitable levels of methane-to-MSA conversion, in the high-pressuregas/liquid mixtures of interest herein, is regarded as a distinct andvaluable discovery in its own right, and discloses a valuable hardwaresystem which can lead to good yields and production rates in a specifictype of highly specialized chemical operation.

6. Three different temperatures (60, 75, and 90 degrees C.) were testedin the “bubble reactor” system that was used during these tests. The 75C tests showed created substantially better results than the 60 C tests,presumably because of the higher reaction kinetics at the highertemperature. However, the 90 C tests indicated lower yields, presumablydue to either or both of: (i) faster decomposition of the radicalinitiators and/or radical species that keep the radical chain reactiongoing; and, or, (ii) faster creation and accumulation of unwanted “chainterminating” species, such as SO2. Therefore, all subsequent tests,using that particular testing equipment, were performed at 75 C.

This is not intended and should not be interpreted as a blanketgenerality, saying that 75° C. will be an optimal temperature when thereaction is scaled up to larger reactor vessels in a pilot plant, or infull-scale manufacturing facilities. Clearly, a range of operatingtemperatures should be tested, any time a processing system has beenfully assembled and is being tested and debugged, for use at a specificsite where the quantity and concentration of any impurities in themethane gas and/or SO3 will generally require that any such processingsystem will need to be tuned, tweaked, and optimized. Accordingly, 75 Cis recommended as a good temperature to commence that type ofoptimization testing, at any specific site, as it approaches actualmanufacturing operations.

7. After the 75 C temperature had been chosen for consistent use in alltests to evaluate and compare other parameters, 2 reactor pressurelevels were tested. Those two pressure levels were 470 pounds per squareinch (psi), and 910 psi (both are “gauge” rather than “absolute”pressure). The 910 psi level gave substantially better results, and wasused in all subsequent tests.

8. It was shown that a first oleum mixture containing 25.2 percent (byweight) of SO3 in sulfuric acid gave slightly higher MSA yields than asecond oleum mixture containing 34.7% SO3, when measured by both (i) SO3conversion percentage (39.2% conversion for the 25% mixture, and 33.9%conversion for the 34% mixture), and (ii) “turnover number” (TON), whichis calculated by dividing conversion percentage, by initiatorequivalents (TONs were 16.4 for the 25% mixture, and 14.1 for the 34%mixture).

Those data points, by themselves, were not sufficient to fully establishthe shape of the yield curve over (and beyond) that range ofconcentrations; however, they were enough to “flag” the importance ofthe SO3 concentration in a solvent, as a parameter which should betested and evaluated at any specific MSA manufacturing site. As ageneral practice, it would be advisable to initially test a range ofconcentrations in 5% stepwise increments (such as 25%, 30%, 35%, 40%,and 45%) at any MSA manufacturing site, to determine the rough shape ofsuch a curve for that site, and to then repeat a set of similar tests,using 1% stepwise increments, over a smaller range which functioned wellin the initial tests, to “nail down” a specific optimal S03 percentageat that site.

9. Direct comparison of “batch” processing versus “continuous flow”processing was done by controlling the “dwell time” of the mixture,inside the pressurized and heated bubble reactors, to be the same amountof time. This was done by taking samples of the reacted product at 3distinct times (after 2 hours and 10 minutes, after 2 hours and 40minutes, and after 3 hours and 10 minutes) under both batch andcontinuous flow conditions. The results indicated that continuous flowprocessing is likely to provide better economic results and higherprofits, at most facilities where the quantity of methane supply issufficient to justify continuous flow (such as at most crude oilproduction facilities in “stranded” locations, where methane that isremoved from the crude oil must be burned in a flare, to get rid of itas a dangerous byproduct of the oil production).

9. It also was confirmed that if the methane-to-MSA reaction is carriedout at high pressure in a solvent mixture that contained SO3 dissolvedin MSA, rather than in sulfuric acid, the yields of MSA were greater.This is consistent with prior statements by the Applicant herein,stating that the oleophilic methyl domain of MSA can help methane gasdissolve into a solution more rapidly.

Designs and Advantages of Tube Reactors

An important point arises from the results described in items 3-5, inthe preceding section. Based on the performance of the lab-scale “tubereactors” described above and in the Examples, it is believed thatcomparable tube reactors—scaled up in size, with larger diameters,longer lengths, and faster flow rates—offer a good design option forcommercial-scale systems, since they offer a number of importantadvantages, including the following:

1. When dealing with highly corrosive liquids, such as sulfuric acid(even if only in relatively small concentrations, such as in a systemwhich uses MSA as the main solvent), the ability to run the radicalchain reaction efficiently, without requiring any type of impeller,stirrer, or other moving part(s) to directly contact the liquid whiledriving a mixing task, can be highly useful and valuable, and cangreatly reduce the number of system shutdowns that will be required,over a span of years or decades, to enable corroded parts to bereplaced.

2. Very long (aggregated) tubes can be placed in relatively compact“cabinet” assemblies (which also can be called shells, cases, cowls,enclosures, or similar terms), by placing linear segments parallel witheach other, inside an outer shell. This design can allow U-shaped jointsto be used to connect the linear segments to each other, at each end ofthe case, with the joints either fully inside the outer shell, orextending slightly outside of it (with sampling ports, injector ports,monitor arrays, etc, if desired, which will be easily and convenientlyaccessible, outside the cabinet).

3. The types of multi-tube “cabinets” discussed above can be designed inany size desired, such as to render it a simple matter to transportseveral of them on a truck, and to move and install any single cabinetusing a forklift.

4. A single cabinet can contain multiple different tube reactors, eachoperating independently of the others, with each tube reactor havingonly some of the linear tube segments in the cabinet. For example, if acabinet contains 48 linear tube segments, stacked together in a 6×8array, they can be operated as 8 different and independent tubereactors, with each tube reactor comprising 6 of the tube segmentsinside that cabinet.

5. If desired, to promote “plug flow”, and to reduce any backflow to anabsolute minimum, a series of flow-constricting devices can be insertedinto the tubes (such as, for example, by designing the U-joints whichconnect the linear segments to have some level of “crimping” of theirinternal flow channels).

6. Use of tube reactors also provides an expanded amount of surfacearea, for cooling purposes, when compared to reactor vessels or chambershaving larger diameters; and, a case or shell which encloses a set oftube segments also can make it easier to pass cooling water around andbetween the reactor tubes, to keep them at desired temperatures despitethe exothermic (i.e., heat-releasing) reactions going on inside them.

7. It also is simple and straightforward to “scale up” a tube reactorsystem, to any desired size or flow rate, by simply installingadditional cabinets containing additional reactor tubes. Furthermore,any additional cabinets do not need to have the same dimensions or flowrates as any prior cabinets, since metering valves and flow-controlmanifolds can be used to allocate any desired flow rate, to any suchcabinet (or to any reactor subassembly, inside any cabinet).

For all of these reasons, tube reactors with passive internal mixingbaffles are believed to provide a practical and useful design for MSAmanufacture, and offer several especially important advantages forscale-up testing and development of commercial-scale methane-to-MSAreactors. In addition, cabinets containing tube reactors are regarded asideal for the initial installation of a first methane-to-MSA “test unit”at any proposed reactor site, since the operation and testing of anysuch cabinet will allow the local owners/operators to reach a better andmore reliable understanding of exactly how the system will work at thatparticular site, and of the types of adjustments, design modifications,and “tweaks” that will allow a custom-designed permanent system to beinstalled at that site, which will be able to provide optimalperformance for decades.

Use of Ozone in MSA Manufacture

While evaluating the data from the continuous-flow tests describedabove, and while pondering and analyzing various issues which relate tooptimal initiator mixtures, the Applicant herein realized that anadditional route to creating initiator mixtures can be provided by theuse of ozone. Although this route may not be optimal for making MSA withvery high purity, it may be able to provide a less-expensive route—whichmay be able to eliminate any need for distillation, leading to largereductions in both fixed costs (for a distillation tower) and operatingcosts (for the energy required to run a distillation tower)—formanufacturing “rough grade” MSA having sufficient purity for at leastsome types of use, such as for processing and reclaiming lead (i.e., themetal) from ores, or from automotive batteries that are being recycled,

As a brief overview, the chemical reactions that are likely to beinvolved are illustrated in FIGS. 5 and 6 herein. As a starting point,ozone (O3) is shaped like a equilateral triangle, where all three of thebond angles are 60 degrees; all bonds are what chemists call “singlebonds”. The 60 degree angles impose serious stresses on the bonds, sincethe “relaxed” angle for bonds is about 110 degrees, a number thatresults from the geometry and tetrahedral arrangement of the “valence”electrons in an atom's outermost “valence shell”, for all elementsheavier than carbon.

Because of those bond stresses, ozone has a powerful tendency to reactwith a very wide variety of “target” molecules (which can also be calledsubstrate molecules, victim molecules, etc.), in a way which “pushes”one of the oxygen atoms, from the ozone, onto the target molecule,thereby allowing the other two oxygen atoms in the ozone reactant toshift back into their normal and “comfortable” arrangement as O2 (i.e.,the type of atmospheric oxygen all animals breathe, where the two atomsare connected to each other via a “double bond”).

In the upper atmosphere, ozone plays a crucial role in protecting theearth from ultraviolet radiation, which would be far more destructiveand toxic if high levels of UV radiation simply passed through the upperatmosphere, and reached the earth's surface, instead of being largelyabsorbed and neutralized by ozone molecules in the upper atmosphere. Thereason why chlorofluorocarbons had to be eliminated from widespread usein air conditioning and refrigeration was because they were damaging theozone layer in the upper atmosphere, leading to dangerously high levelsof destructive UV radiation reaching the earth's surface.

However, at or near ground level, ozone is dangerous and destructive. Itwill attack and oxidize nearly anything that is not metallic, such asplant leaves, animal lungs, and anything made of rubber or plastic. Evenvery low levels of ozone, at ground level, will cause the rubber in autoand truck tires to become cracked, brittle, and weakened, over a span ofyears.

Accordingly, when ozone reacts with a molecule, it usually does so byeffectively pushing one of its oxygen atoms onto the “target” molecule,thereby causing an oxidation reaction, which in natural settings almostalways degrades and damages the target molecule(s). However, that sameproperty makes ozone highly useful, as a gaseous oxidizing agent, incertain types of chemical manufacturing operations where the ozone istightly controlled, and prevented from escaping into the atmosphere.

Indeed, an important parallel, and an important difference, should benoted, between ozone, and hydrogen peroxide. Both compounds are strongoxidizing agents, since they both are small molecules with an “extra”oxygen atom which both of them are, in effect, trying to get rid of, toreach a more “stable and standard” condition (H2O2 can become water bygetting rid of an oxygen, while ozone becomes O2 molecules, which makeup about 20% of earth's atmosphere). Importantly, by NOT creating wateras a byproduct when it manages to get rid of its third oxygen, ozone canmake a better (or at least “better behaved”) oxidizing agent, than H2O2.As one example, ozone (as a gas which leaves no residue) is often usedto get rid of severely bad smells, as might occur if someone unwittinglyleft some rotting food in a closed and locked car, for a week, during ahot summer month. That method of using a dry gas, to remove a stenchfrom a complex and multi-surfaced car interior, is far more convenientand effective than trying to scrub down a car interior with hydrogenperoxide.

In the methane-to-MSA pathways that are of interest herein, there aretwo likely pathways that ozone might create and use, as illustrated inFIGS. 4 and 5. Both pathways are likely to occur, at some level, in amixture that contains the combination of molecules that will becontained inside the MSA-forming reactor (or in a stream which leadsinto that reactor), and the overall results will be the same regardlessof which pathway is followed, since both of them create and then consumemono-methyl-Marshall's acid as an intermediate compound.

As illustrated in FIG. 4, which depicts “Possible Ozone Pathway #1”, amolecule of ozone will react with SO3, to create an unstable andtransitory intermediate, having a ring structure containing a sulfuratom and four oxygen atoms. A molecule of ionic MSA (with the hydrogenproton dissociated from the hydroxy group) can react with that ringstructure, to create methyl-Marshall's acid while releasing an oxygenmolecule (O2). As described above, when the peroxide bond of themethyl-Marshall's acid is broken, it will release both:

(i) one MSA radical, which has the proper strength to remove a hydrogenatom (both proton and electron) from a fresh methane molecule, therebycreating stable MSA and a new methyl radical, which will then combinewith SO3 to create another MSA radical, to keep the radical chainreaction going; and,

(ii) a sulfuric acid radical, which also has the proper strength toremove a hydrogen atom (both proton and electron) from a fresh methanemolecule, thereby creating both stable sulfuric acid and a new methylradical, which will then combine with SO3 to create another MSA radical,to keep the radical chain reaction going.

Accordingly, when methylMarshall's acid breaks apart, it will triggerthe formation of not just one but two methyl radicals, both of which caninitiate new chain reactions that can continue for multiple cycles,creating more MSA. And, since ozone is believed likely to be capable ofconverting at least some quantity of sulfur trioxide and MSA intomethylMarshall's acid, ozone may be able to provide a useful andefficient way to convert additional quantities of methane gas into MSA.

In “Possible Ozone Pathway #2”, illustrated in FIG. 5, a molecule ofozone can react with MSA, to create methyl-Caro's acid, which can thenreact with SO3, to create the exact same intermediate described above,methylMarshall's acid, which will then break apart to release tworadicals. Each of those two radicals can then initiate a radical chainreaction which can continue for a large number of cycles, convertingmethane into MSA by combining it with SO3.

In summary, by using either or both of the two candidate pathways shownin the drawings, ozone can cause SO3 and MSA to combine with each other,to form a potent and useful intermediate compound (i.e.,methylMarshall's acid), which can then serve as a “primary” initiatorcompound (as described above), which will trigger not just one but twoparallel-acting copies of the radical chain reaction which will convertmethane into MSA.

EXAMPLES Example 1: Preparation of Mecaro's Acid (Methyl Sulfonyl PeroxyAcid, MSPA)

The tests and results described in Examples 1-4 herein were initiallydescribed in U.S. provisional application 62/601,065, filed on Mar. 10,2017, in Examples 1 & 2 therein. The description below has been expandedsomewhat, to provide more information on exactly how these tests werecarried out, and how the analytical work was performed.

As described above, the compound known as Methyl-Caro's Acid (alsowritten as meCaro's, with the alternate name “Methyl Sulfonyl PeroxyAcid” (MSPA) can be added in relatively small quantities to a mixture ofother sulfur-peroxide compounds that are being used to initiate theradical chain reaction which converts methane gas, into MSA, inside areactor vessel. When added in that manner, the methyl-Caro's acid canserve as a potent oxidizing agent, to convert molecules of sulfurDI-oxide (SO2, an unwanted chain-terminating molecule) into SO3 (i.e.,sulfur TRI-oxide, a desired and essential component of the radical chainreaction).

Accordingly, as illustrated in the chemical reaction shown in FIG. 1B,to synthesize meCaro's acid, a mixture of 5 ml of 100% methane-sulfonicacid (MSA) and 5 ml of concentrated (fuming) sulfuric acid was createdin an Erlenmeyer flask that was partially submerged in ice water.Vigorous stirring was commenced, using a magnetic stirring bar, and 0.5ml of 50% (w/w) hydrogen peroxide was slowly added.

Example 2: 91% Yield of MSA when Mecaro's Acid Used as Initiator

A 100-mL glass-lined high-pressure Parr autoclave reactor, equipped witha magnetic stirring bar, was loaded with 1.7 grams of SO3 in 4 grams ofH2SO4. 0.4 mmol of the initiator solution (prepared as described above,containing meCaro's acid) was added. The reactor was purged withnitrogen gas (N2), then pressurized with methane gas (CH4) until apressure of 100 “bar” (i.e., 100 times normal atmospheric (barometric)pressure) was reached. The reactor was heated to 55 C, with stirring.When measured after 4 hours, the pressure had dropped to 38 bar.

Surplus water was added, to convert unreacted SO3 to sulfuric acid. Theliquid mixture of MSA, sulfuric acid, and water was then passed througha Dionex-100 ion chromatograph, using an AS4 column(www.thermofisher.com/order/catalog/product/035311). That type of ionexchange column converts sulfuric acid into the sodium sulfate salt, andit converts MSA into the sodium mesylate salt. Those two salts passthrough the column at different rates, and the analytical components ofthe control unit calculate the “area” of each peak that emerges,allowing for quantitative analysis of the different salts (whichprovides a quantitative measurement of the acids which created thosesalts). Based on the data from both (i) the pressure drop, in thereactor vessel, and (i) the quantitative analysis by chromatography, thecalculated yield of MSA was 91% (i.e., 91% of the SO3, the limitingreagent in the closed batch reactor, apparently had been converted intoMSA). In addition, using those data, the quantity of MSA was calculatedto be about 40%, by weight, of the combined weight of the MSA, sulfuricacid, and SO3 mixture, before water was added to the mixture to convertthe SO3 to sulfuric acid.

Example 3: Synthesis of Methyl-Sulfonyl-Peroxo-Sulfuric Acid(MeMarshall's Acid)

To synthesize meMarshall's acid, a mixture of 4 ml of 100%methane-sulfonic acid (MSA) and 6 ml of concentrated (fuming) sulfuricacid was created in an Erlenmeyer flask that was partially submerged inice water. Vigorous stirring was commenced, using a magnetic stirringbar, and 0.5 ml of 50% (w/w) hydrogen peroxide was slowly added. Thiscreated the same compound described in Example 1 (i.e., methyl-Caro'sacid), as an intermediate. After 20 minutes, 2.5 ml of 30% oleum (i.e.,30% S03 and 70% sulfuric acid, by weight) was added dropwise, withvigorous stirring.

Example 4: 90% Yield of MSA when MeMarshall's Acid Used as BatchInitiator

The same procedures described in Example 2 were used, to evaluatemeMarshall's acid (prepared as described in Example 3) as an initiatorfor the methane-to-MSA reaction. 1.7 grams of SO3 in 4 grams of H2SO4were used, along with 0.4 mmol of the meMarshall's initiator.

When measured after 4 hours, the pressure inside the high-pressurereactor had dropped from 100 bar, to 37 bar. The yield (based on initialSO3 content) was 90%, and the amount of methane sulfonic acid (in theMSA, sulfuric acid, and SO3 mixture) was about 40% by weight.

Example 5: MSA Formation by Methyl-Marshall's Acid when No Sulfuric Acidwas Present (Use of MSA as Solvent)

The assertion set forth in Examples 3 and 4—that meMarshall's acid was agood initiator for the radical chain reaction that created MSA—could bechallenged, by someone who might assert and argue that: (i) the role ofmeMarshall's acid, in creating the MSA, was not fully and conclusivelyproven, because alternate possible contributing factors, pathways, orreagents were not fully eliminated as agents which might havecontributed to MSA formation; and, (ii) the presence of any sulfuricacid, under the conditions involved in Examples 3 and 4, might offer aplausible alternate pathway to MSA formation, which would not requiremeMarshall's acid.

Although not initially planned with that goal in mind, the Applicantlater realized that a different experiment, done for an entirelydifferent reason, offers solid evidence that:

(i) meMarshall's acid was indeed made, by a different process which didnot include or involve any sulfuric acid, except in very small “traceamounts”; and,

(ii) the meMarshall's acid was indeed a good “primary initiator”, in theabsence of any significant quantity of sulfuric acid.

That experiment was initially intended to directly compare thequantities of MSA that were created, under identical conditions (usingthe exact same reactor device, at identical temperatures (75 C) andpressures (930 lb/square inch)), using either of two different solvents,which were:

(1) solvent 1, which was a 33.4% preparation of the mixture called“oleum” (i.e., containing 33.4% SO3, as a weight percentage, inconcentrated sulfuric acid); versus,

(2) solvent 2, which was 25.9% SO3, in liquid MSA rather than sulfuricacid.

In Run #1, using solvent 1 (oleum) in an ice bath, hydrogen peroxide(H₂O₂) was added to the mixture at 2.5 mole percent. The H2O2 reagentconverted a portion of the sulfuric acid initially into Caro's acid;most of the Caro's acid then reacted with SO3, in the oleum component,to create Marshall's acid. After a delay for mixing and reaction, 12mole % MSA was then added, as a solvent to help solubilize methane gasin the liquid. If there was any unreacted Caro's acid left in themixture when the MSA was added, it might possibly have reacted with theMSA; however, because of the large excess of SO3 that was mixed with theCaro's acid, it is believed that essentially all of the Caro's acid andH2O2 had been consumed, before any MSA was added. The resultinginitiator mixture was then continuously injected, using a syringe pump,over a span of 2 hours, into a heated and pressurized mixture of methaneand oleum (containing 33.4 mol percent SO3 in sulfuric acid, at 75 C and930 psi). The net result of that test run was that 39% of the SO3reagent was converted into MSA, as analyzed by 1H-NMR, using deuteratedacetic acid as an internal standard.

By contrast, in Run #2 (using solvent 2, MSA), 25.9 mol percent SO3 wasdissolved in MSA with continuous stirring, at 17 degrees C. H2O2 wasthen added (at 2.5 mole percent) to that mixture, which contained nosulfuric acid. The H2O2 converted a portion of the MSA into methylCaro'sacid, and the SO3 reacted with the methylCaro's acid, to convert it into(mono)methylMarshall's acid. The resulting mixture, containing(mono)methylMarshall's acid, was continuously injected, using a syringepump, over a span of 2 hours, into a heated and pressurized mixture ofmethane, and MSA containing 25.9 mol percent SO3, at 75 C and 930 psi.

The net result of Test Run 2 was that 44% of the SO3 reagent wasconverted into MSA, as analyzed by 1H-NMR, using deuterated acetic acidas an internal standard. The increase of 5% (from 39% in Run 1, to 44%in Run 2) is noteworthy, since there was a lower concentration of SO3 inthe Run 2 mixture. Since SO3 is the most expensive reagent in themixture, the ability of the MSA solvent system to make more efficientuse of the SO3 reagent is regarded as an important confirmation of thereaction system disclosed herein.

It should be noted that a very small quantity of sulfuric acid wascreated, after breakage of the peroxide bond in the(mono)methylMarshall's acid, because a sulfuric acid radical is releasedby one side of the (mono)methylMarshall's acid, when that bond isbroken, and that sulfuric acid radical will extract a hydrogen atom,from a fresh methane molecule. However, that reaction happens only once,in a manner which triggers a chain reaction that will carry on fordozens or hundreds of additional cycles without creating any additionalsulfuric acid molecules. Accordingly, any trace concentration ofsulfuric acid in the mixture was much too low to account for the 44%conversion level noted above.

Example 6: Design and Testing of Tube Reactor System

As described above, under the heading, “Continuous Flow Tests andResults”, the Applicant herein hired and paid an independent consultingfirm to perform a number of tests, in ways which generated objective andimpartial data which both he and a licensee company analyzed and reliedupon, during licensing negotiations. That consulting firm specializes inbenchtop testing of chemical reaction pathways that have been shown towork in “batch reactor” settings, using continuous flow methods andequipment. As an overview of several major points, which are discussedin more detail in the narrative description above:

(1) Those tests indicated that a series of “tube reactors”, operating insequence and containing passive/static/inert mixing baffles inside them,were well-suited for carrying out the reaction, and apparently couldestablish a desirable type of “plug flow” of the high-pressuregas/liquid mixture through the tubes, with few if any problems ofbackflow, stagnant zones, backward permeation of chain terminatingspecies, etc.

(2) “Frit” devices (i.e., porous discs or filters that are used todisperse and distribute a gas which is being pumped into a liquid)performed better when they had pore sizes of 10 microns, rather than 40microns.

(3) Tests also indicated that passage of the pressurized gas/liquidmixture through a sequence of tubes, in a serial arrangement where themixture had to pass through a series of enlarged tubes coupled to eachother by narrow tubing, also promoted better yields, presumably due tothe additional mixing that occurred each time the mixture adapted to achange in internal diameter in the processing system.

6. Three operating temperatures (60, 75, and 90 degrees C.) werecompared against each other, and the 75 C temperature performed bestfrom among those candidates.

7. Two pressure levels were tested, which were 470 and 910 pounds persquare inch (psi, “gauge” pressure). The 910 psi pressure gave betterresults.

8. Test results also indicated that if the methane-to-MSA reaction wascarried using SO3 dissolved in MSA rather than in sulfuric acid, theyields of MSA were greater.

Example 7: Preparation of DMSP by Electrolysis

A flow-through electrolysis cell was constructed to make DMSP byelectrolysis of pure MSA. The cell was sized to be large enough to ableto produce enough MSA to feed an MSA pilot reactor and designed to bescalable to a commercial unit. The cell components consisted of a singleanode (active on both sides), surrounded by two cathodes. Gaskets wereused to form a gap and make a seal between the anodes and cathodes, andtwo cell bodies with machined ports and flow chambers allowedelectrolyte to enter the gap between the electrodes on one end, and exiton the other end. Tubing and fittings allowed the MSA electrolyte to befed through the cell on a continuous basis, from a pump, and additionalhardware allowed the components to be bolted together in aplate-and-frame type of assembly.

The anode was platinum foil, fastened to a titanium substrate whichcarried electric current from wires connected to a 7-volt DC powersupply. The substrate and foil, together, distributed the voltage andcurrent throughout the surface area of the platinum. The cathodes weremade of stainless steel mesh, and the cell bodies and gaskets were madeof TEFLON polymer.

The cell was connected to a 50 ampere power supply and fed with pure MSAsolution, with 1-2% water added to improve conductivity. The electrolytewas fed from a one liter beaker as a continuous recirculating stream ata flow rate of 1.0-1.5 liters per minute. Feed was from the beaker tothe bottom of the cell, and exit was from the top of the cell back tothe beaker. The beaker was immersed in a water bath to remove the heatof electrolysis and maintain the temperature of the electrolyte.

Several tests were done at cell temperatures between 25-45 C, makingDMSP concentrations of between 20 and 100 g/l. Concentration of DMSP wasanalyzed by iodometric titration.

The DMSP-MSA mixture from the cell was cooled to 10-20 C in an ice bath.DMSP precipitated out, and was separated from the solution using ascreen filter. Solid DMSP was removed from the screen filter, and wasredissolved in MSA, up to concentrations of 200 g/l DMSP. Those mixtureswere tested as initiators for MSA formation, as described in the nextexample.

Example 8: Use of DMSP as Initiator to Make MSA

26.0 moles H2SO4, 11.7 moles of S03, and 14.4 moles of MSA were added toa stirred Parr reactor, and the reactor was pressurized with methane to1000 psig. 0.46 mol/l of DMSP (made as described in the previousexample) was injected into the reactor over a span of 2 hours, at a feedrate of 0.6 liter/hour, for a total DMSP feed of 1200 ml.

The pressure inside the vessel began to drop shortly after the DMSPinjection was commenced, due to the conversion of methane gas intoliquid MSA. Additional methane was subsequently injected into thereactor at a rate of 4.0-9.8 liter/min, as measured with a Brooks massflow meter, to maintain the pressure. A total of 11.2 moles of methanewas fed over the 2-hour test run. The composition of reactor product was26.0 moles H2SO4, 0.5 moles S03, and 26.1 moles of MSA at the end of the2 hour reaction period. Reactor analysis for DMSP content, half an hourafter the DMSP injection was terminated, indicated that less than 0.1gram of DMSP remained, per liter of liquid. This indicated that the DMSPhad been thoroughly consumed.

Thus, there has been shown and described an improved method for creatingMSA from methane, using mixture of both “primary” initiator compounds,which can initiate the radical chain reaction disclosed herein, and“extender” initiator compounds, which can eliminate or reduce SO2 orother “chain terminating” species which would otherwise interfere withand truncate the chain reaction. Although this invention has beenexemplified for purposes of illustration and description by reference tocertain specific embodiments, it will be apparent to those skilled inthe art that various modifications, alterations, and equivalents of theillustrated examples are possible. Any such changes which derivedirectly from the teachings herein, and which do not depart from thespirit and scope of the invention, are deemed to be covered by thisinvention.

REFERENCES

-   Korth, H. G. et al, “Direct spectroscopic detection of sulfonyloxyl    radicals and first measurements of their absolute reactivities,” J.    Phys. Chem. 94: 8835-8839 (1990)-   Robinson, E. A., et al, “The reaction of methanesulfonic acid with    sulfur trioxide,” Canadian J. Chemistry 44: 1437-1444 (1966)

The invention claimed is:
 1. A method for producing methane-sulfonicacid from methane and sulfur trioxide using methane sulfonic acid,sulfuric acid or a combination thereof as a solvent which comprisesperforming a radical chain reaction by introducing a first gas/liquidmixture comprising sulfur trioxide reagent and methane into a reactorvessel continuously with a second mixture comprising: (i) at least oneprimary initiator compound having a peroxide bond which when broken willrelease radical species capable of efficiently removing hydrogen atomsfrom at least one hydrocarbon or carbohydrate reagent, wherein saidprimary initiator compound is selected from the group consisting ofmethyl-Marshall's acid (methyl-sulfonyl-peroxo-sulfuric acid), anddimethyl-Marshall's acid (dimethyl-sulfonyl-peroxide), and combinationsthereof; and, (ii) methyl-Caro's acid (methyl-sulfonyl-peroxy-acid) asan extender initiator having a peroxide bond which, when broken apart,will release at least one radical species that will oxidize sulfurdioxide molecules into sulfur trioxide molecules wherein the quantity ofsaid extender initiator is in the range of from 2% to 10% of the totalinitiator weight, and wherein said reactor vessel comprises a tubeenclosure with at least one internal static mixing baffle configured forprocessing the gas/liquid mixture that flows through said tube enclosureat a pressure in the range of from 470 psi to 1500 psi and a temperaturein the range of from 60° C. to 90° C. under plug flow conditions withthe result that methane-sulfonic acid in liquid form is recovered fromthe reactor vessel.
 2. The method of claim 1 wherein said reactor vesselcomprises multiple linear segments of tubing, coupled together to createa continuous flow path through multiple tubing segments.
 3. The methodof claim 1 or claim 2 wherein (i) said extender initiator is injectedseparately into the reactor vessel but continuously while said primaryinitiator is introduced into the reactor vessel or (ii) said extenderinitiator is injected intermittently into the reactor vessel while saidprimary initiator is introduced into the reactor vessel.
 4. The methodof claim 1 or claim 2 wherein said first gas/liquid mixture comprisingsulfur trioxide reagent and methane is introduced into said reactorvessel continuously with: (i) the at least one primary initiatorcompound, and (ii) the extender initiator is generated within thereactor vessel.
 5. The method of claim 1 or claim 2 wherein said secondmixture comprises: (i) methyl-Marshall's acid(methyl-sulfonyl-peroxo-sulfuric acid), and (ii) methyl-Caro's acid(methyl-sulfonyl-peroxy-acid) that is formed by mixing H₂O₂ with methanesulfonic acid and then adding SO₃ to the resulting mixture wherein theSO₃ is added at no more than a molar equivalent of the amount ofmethyl-Marshall's acid in the mixture.